Some minor optimizations

Author: manlge

README.md

@@ -67,6 +67,7 @@ prettytable-rs="0.8.0"
 ```
 ## Example
 
+```rust
 use std::vec;
 
 use chrono;
@@ -401,3 +402,4 @@ fn create_tablet(row_count: i32, start_timestamp: i64) -> Tablet {
     });
     tablet
 }
+```

src/client/remote.rs

@@ -240,8 +240,8 @@ impl<'a> RpcDataSet<'a> {
         if self.closed {
             return false;
         }
-        if let Some(session_id) = self.session.session_id {
-            if self.query_data_set.time.len() == 0 {
+        if self.query_data_set.time.len() == 0 {
+            if let Some(session_id) = self.session.session_id {
                 //Fetching result from iotdb server
                 match self
                     .session
@@ -306,10 +306,8 @@ impl<'a> RpcDataSet<'a> {
                     }
                 }
             }
-            self.query_data_set.time.len() > 0
-        } else {
-            return false;
         }
+        self.query_data_set.time.len() > 0
     }
 }