[Feat] Add streaming agents (#277)

* format

* fix ReAct

* support streaming agents

* fix type hints

* update

Author: braisedpork1964

README.md

@@ -96,7 +96,7 @@ print(dumped_memory['memory'])
 Clear the memory of this session(`session_id=0` by default):
 
 ```python
-agent.memory.reset()
+agent.reset()
 ```
 
 ### Custom Message Aggregation

lagent/agents/__init__.py

@@ -1,9 +1,33 @@
-from .agent import Agent, AgentDict, AgentList, AsyncAgent, AsyncSequential, Sequential
+from .agent import (
+    Agent,
+    AgentDict,
+    AgentList,
+    AsyncAgent,
+    AsyncSequential,
+    AsyncStreamingAgent,
+    AsyncStreamingSequential,
+    Sequential,
+    StreamingAgent,
+    StreamingSequential,
+)
 from .react import AsyncReAct, ReAct
 from .stream import AgentForInternLM, AsyncAgentForInternLM, AsyncMathCoder, MathCoder
 
 __all__ = [
-    'Agent', 'AgentDict', 'AgentList', 'AsyncAgent', 'AgentForInternLM',
-    'AsyncAgentForInternLM', 'MathCoder', 'AsyncMathCoder', 'ReAct',
-    'AsyncReAct', 'Sequential', 'AsyncSequential'
+    'Agent',
+    'AgentDict',
+    'AgentList',
+    'AsyncAgent',
+    'AgentForInternLM',
+    'AsyncAgentForInternLM',
+    'MathCoder',
+    'AsyncMathCoder',
+    'ReAct',
+    'AsyncReAct',
+    'Sequential',
+    'AsyncSequential',
+    'StreamingAgent',
+    'StreamingSequential',
+    'AsyncStreamingAgent',
+    'AsyncStreamingSequential',
 ]