fix: Fixes the identity prompt to be one line and add ending period after description statement

From ``` You are an agent. Your internal name is "agent". The description about you is "test description" ``` to ``` You are an agent. Your internal name is "agent". The description about you is "test description". ``` PiperOrigin-RevId: 822358196

Author: Jacksunwei

src/google/adk/flows/llm_flows/identity.py

@@ -34,10 +34,10 @@ async def run_async(
  self, invocation_context: InvocationContext, llm_request: LlmRequest
  ) -> AsyncGenerator[Event, None]:
  agent = invocation_context.agent
- si = [f'You are an agent. Your internal name is "{agent.name}".']
+ si = f'You are an agent. Your internal name is "{agent.name}".'
  if agent.description:
- si.append(f' The description about you is "{agent.description}"')
- llm_request.append_instructions(si)
+ si += f' The description about you is "{agent.description}".'
+ llm_request.append_instructions([si])
 
  # Maintain async generator behavior
  if False: # Ensures it behaves as a generator

tests/unittests/flows/llm_flows/test_identity.py

@@ -64,7 +64,8 @@ async def test_with_description():
  ):
  pass
 
- assert request.config.system_instruction == "\n\n".join([
- 'You are an agent. Your internal name is "agent".',
- ' The description about you is "test description"',
- ])
+ assert (
+ request.config.system_instruction
+ == """\
+You are an agent. Your internal name is "agent". The description about you is "test description"."""
+ )