doc: add section titles

Signed-off-by: ekexium <ekexium@gmail.com>

src/config.rs

@@ -38,6 +38,7 @@ impl Config {
     /// It's important to **include more than one PD endpoint** (include all, if possible!)
     /// This helps avoid having a *single point of failure*.
     ///
+    /// # Examples
     /// ```rust
     /// # use tikv_client::Config;
     /// let config = Config::new(vec!["192.168.0.100:2379", "192.168.0.101:2379"]);
@@ -58,6 +59,7 @@ impl Config {
     /// By default, TiKV connections do not utilize transport layer security. Enable it by setting
     /// these values.
     ///
+    /// # Examples
     /// ```rust
     /// # use tikv_client::Config;
     /// let config = Config::new(vec!["192.168.0.100:2379", "192.168.0.101:2379"]).with_security(

src/kv/bound_range.rs

@@ -30,6 +30,7 @@ use tikv_client_proto::kvrpcpb;
 /// `impl Into<Key>`. You can implement `Into<BoundRange>` for your own types by using `try_from`.
 ///
 ///
+/// # Examples
 /// ```rust
 /// # use std::ops::{Range, RangeInclusive, RangeTo, RangeToInclusive, RangeFrom, RangeFull, Bound};
 /// # use std::convert::TryInto;
@@ -83,6 +84,7 @@ impl BoundRange {
     ///
     /// The **end** of a scan is exclusive, unless appended with an '\0', then it is inclusive.
     ///
+    /// # Examples
     /// ```rust
     /// use tikv_client::{BoundRange, Key, ToOwnedRange};
     /// // Exclusive

src/kv/key.rs

@@ -20,6 +20,7 @@ const _PROPTEST_KEY_MAX: usize = 1024 * 2; // 2 KB
 ///
 /// This type wraps around an owned value, so it should be treated it like `String` or `Vec<u8>`.
 ///
+/// # Examples
 /// ```rust
 /// use tikv_client::Key;
 ///
@@ -43,6 +44,7 @@ const _PROPTEST_KEY_MAX: usize = 1024 * 2; // 2 KB
 /// isn't able to determine the correct type. Notably in the `assert_eq!()` and `==` cases. In
 /// these cases using the fully-qualified-syntax is useful:
 ///
+/// # Examples
 /// ```rust
 /// use tikv_client::Key;
 ///

src/kv/kvpair.rs

@@ -8,6 +8,7 @@ use tikv_client_proto::kvrpcpb;
 
 /// A key/value pair.
 ///
+/// # Examples
 /// ```rust
 /// # use tikv_client::{Key, Value, KvPair};
 /// let key = "key".to_owned();

src/kv/value.rs

@@ -12,6 +12,7 @@ const _PROPTEST_VALUE_MAX: usize = 1024 * 16; // 16 KB
 ///
 /// This type wraps around an owned value, so it should be treated it like `String` or `Vec<u8>`.
 ///
+/// # Examples
 /// ```rust
 /// use tikv_client::Value;
 ///
@@ -35,6 +36,7 @@ const _PROPTEST_VALUE_MAX: usize = 1024 * 16; // 16 KB
 /// isn't able to determine the correct type. Notably in the `assert_eq!()` and `==` cases. In
 /// these cases using the fully-qualified-syntax is useful:
 ///
+/// # Examples
 /// ```rust
 /// use tikv_client::Value;
 ///

src/raw/client.rs

@@ -27,6 +27,7 @@ pub struct Client {
 impl Client {
     /// Create a raw [`Client`](Client).
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Config, RawClient};
     /// # use futures::prelude::*;
@@ -52,6 +53,7 @@ impl Client {
     ///
     /// For normal users of the raw API, you don't need to use other column families.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Config, RawClient, ColumnFamily};
     /// # use futures::prelude::*;
@@ -79,6 +81,7 @@ impl Client {
     ///
     /// By default, `key_only` is set to false.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Config, RawClient, ToOwnedRange};
     /// # use futures::prelude::*;
@@ -102,6 +105,7 @@ impl Client {
     ///
     /// Retuning `Ok(None)` indicates the key does not exist in TiKV.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Value, Config, RawClient};
     /// # use futures::prelude::*;
@@ -125,6 +129,7 @@ impl Client {
     ///
     /// Non-existent entries will not appear in the result. The order of the keys is not retained in the result.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{KvPair, Config, RawClient};
     /// # use futures::prelude::*;
@@ -148,6 +153,7 @@ impl Client {
     ///
     /// Once resolved this request will result in the setting of the value associated with the given key.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Key, Value, Config, RawClient};
     /// # use futures::prelude::*;
@@ -169,6 +175,7 @@ impl Client {
     ///
     /// Once resolved this request will result in the setting of the values associated with the given keys.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Error, Result, KvPair, Key, Value, Config, RawClient, ToOwnedRange};
     /// # use futures::prelude::*;
@@ -196,6 +203,7 @@ impl Client {
     ///
     /// It does not return an error if the key does not exist in TiKV.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Key, Config, RawClient};
     /// # use futures::prelude::*;
@@ -218,6 +226,7 @@ impl Client {
     ///
     /// It does not return an error if some of the keys do not exist and will delete the others.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Config, RawClient};
     /// # use futures::prelude::*;
@@ -238,6 +247,7 @@ impl Client {
     ///
     /// Once resolved this request will result in the deletion of all keys lying in the given range.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Key, Config, RawClient, ToOwnedRange};
     /// # use futures::prelude::*;
@@ -262,6 +272,7 @@ impl Client {
     /// only the first `limit` pairs are returned, ordered by the key.
     ///
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{KvPair, Config, RawClient, ToOwnedRange};
     /// # use futures::prelude::*;
@@ -296,6 +307,7 @@ impl Client {
     /// As a result, you may get **more than** `each_limit` key-value pairs for each range.
     /// But you should not miss any entries.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Key, Config, RawClient, ToOwnedRange};
     /// # use futures::prelude::*;

src/raw/mod.rs

@@ -30,6 +30,7 @@ mod requests;
 ///
 /// The best (and only) way to create a [`ColumnFamily`](ColumnFamily) is via the `From` implementation:
 ///
+/// # Examples
 /// ```rust
 /// # use tikv_client::ColumnFamily;
 /// # use std::convert::TryFrom;

src/transaction/client.rs

@@ -43,6 +43,7 @@ pub struct Client {
 impl Client {
     /// Creates a transactional [`Client`](Client).
     ///
+    /// # Examples
     /// ```rust,no_run
     /// use tikv_client::{Config, TransactionClient};
     /// use futures::prelude::*;
@@ -76,6 +77,7 @@ impl Client {
     ///
     /// For details, check our [SIG-transaction](https://github.com/tikv/sig-transaction/tree/master/doc/tikv#optimistic-and-pessimistic-transactions).
     ///
+    /// # Examples
     /// ```rust,no_run
     /// use tikv_client::{Config, TransactionClient};
     /// use futures::prelude::*;
@@ -97,6 +99,7 @@ impl Client {
     /// Write operations will lock the data until commit, thus commit requests should not suffer from write conflict.
     /// For details, check our [SIG-transaction](https://github.com/tikv/sig-transaction/tree/master/doc/tikv#optimistic-and-pessimistic-transactions).
     ///
+    /// # Examples
     /// ```rust,no_run
     /// use tikv_client::{Config, TransactionClient};
     /// use futures::prelude::*;
@@ -120,6 +123,7 @@ impl Client {
 
     /// Retrieves the current [`Timestamp`](Timestamp).
     ///
+    /// # Examples
     /// ```rust,no_run
     /// use tikv_client::{Config, TransactionClient};
     /// use futures::prelude::*;

src/transaction/transaction.rs

@@ -32,6 +32,7 @@ use tikv_client_proto::{kvrpcpb, pdpb::Timestamp};
 /// provides materials explaining designs and implementations of multiple features in TiKV transactions.
 ///
 ///
+/// # Examples
 /// ```rust,no_run
 /// use tikv_client::{Config, TransactionClient};
 /// use futures::prelude::*;
@@ -104,6 +105,7 @@ impl Transaction {
     ///
     /// It can only be used in pessimistic mode.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Value, Config, TransactionClient};
     /// # use futures::prelude::*;
@@ -139,6 +141,7 @@ impl Transaction {
     ///
     /// Non-existent entries will not appear in the result. The order of the keys is not retained in the result.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Key, Value, Config, TransactionClient};
     /// # use futures::prelude::*;
@@ -177,6 +180,7 @@ impl Transaction {
     ///
     /// Non-existent entries will not appear in the result. The order of the keys is not retained in the result.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Key, Value, Config, TransactionClient};
     /// # use futures::prelude::*;
@@ -216,6 +220,7 @@ impl Transaction {
     /// If the number of eligible key-value pairs are greater than `limit`,
     /// only the first `limit` pairs are returned, ordered by the key.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Key, KvPair, Value, Config, TransactionClient};
     /// # use futures::prelude::*;
@@ -254,12 +259,13 @@ impl Transaction {
     /// Create a 'scan_reverse' request.
     ///
     /// Similar to [`scan`](Transaction::scan), but in the reverse direction.
-    fn scan_reverse(&self, _range: impl RangeBounds<Key>) -> BoxStream<Result<KvPair>> {
+    pub(crate) fn scan_reverse(&self, _range: impl RangeBounds<Key>) -> BoxStream<Result<KvPair>> {
         unimplemented!()
     }
 
     /// Sets the value associated with the given key.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Key, Value, Config, TransactionClient};
     /// # use futures::prelude::*;
@@ -286,6 +292,7 @@ impl Transaction {
     ///
     /// Deleting a non-existent key will not result in an error.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Key, Config, TransactionClient};
     /// # use futures::prelude::*;
@@ -316,6 +323,7 @@ impl Transaction {
     ///
     /// In pessimistic mode, please use [`get_for_update`](Transaction::get_for_update) instead.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Config, TransactionClient};
     /// # use futures::prelude::*;
@@ -336,6 +344,7 @@ impl Transaction {
 
     /// Commits the actions of the transaction.
     ///
+    /// # Examples
     /// ```rust,no_run
     /// # use tikv_client::{Config, TransactionClient};
     /// # use futures::prelude::*;