Invalid role when using chat history with Google Gemini LLM model

[Stanley00]

When using Gemini as LLM model for Assistant, I got this error:

Traceback (most recent call last):
  File "./example", line 11, in <module>
    assistant.print_response("What if I replace 10 by 8 in previous message?")
  File "$VENV_PATH/lib/python3.10/site-packages/phi/assistant/assistant.py", line 1476, in print_response
    for resp in self.run(message=message, messages=messages, stream=True, **kwargs):
  File "$VENV_PATH/lib/python3.10/site-packages/phi/assistant/assistant.py", line 894, in _run
    for response_chunk in self.llm.response_stream(messages=llm_messages):
  File "$VENV_PATH/lib/python3.10/site-packages/phi/llm/google/gemini.py", line 273, in response_stream
    for response in self.invoke_stream(messages=messages):
  File "$VENV_PATH/lib/python3.10/site-packages/phi/llm/google/gemini.py", line 138, in invoke_stream
    yield from self.client.generate_content(
  File "$VENV_PATH/lib/python3.10/site-packages/google/generativeai/generative_models.py", line 325, in generate_content
    iterator = self._client.stream_generate_content(
  File "$VENV_PATH/lib/python3.10/site-packages/google/ai/generativelanguage_v1beta/services/generative_service/client.py", line 1134, in stream_generate_content
    response = rpc(
  File "$VENV_PATH/lib/python3.10/site-packages/google/api_core/gapic_v1/method.py", line 131, in __call__
    return wrapped_func(*args, **kwargs)
  File "$VENV_PATH/lib/python3.10/site-packages/google/api_core/retry/retry_unary.py", line 293, in retry_wrapped_func
    return retry_target(
  File "$VENV_PATH/lib/python3.10/site-packages/google/api_core/retry/retry_unary.py", line 153, in retry_target
    _retry_error_helper(
  File "$VENV_PATH/lib/python3.10/site-packages/google/api_core/retry/retry_base.py", line 212, in _retry_error_helper
    raise final_exc from source_exc
  File "$VENV_PATH/lib/python3.10/site-packages/google/api_core/retry/retry_unary.py", line 144, in retry_target
    result = target()
  File "$VENV_PATH/lib/python3.10/site-packages/google/api_core/timeout.py", line 120, in func_with_timeout
    return func(*args, **kwargs)
  File "$VENV_PATH/lib/python3.10/site-packages/google/api_core/grpc_helpers.py", line 174, in error_remapped_callable
    raise exceptions.from_grpc_error(exc) from exc
google.api_core.exceptions.InvalidArgument: 400 Please use a valid role: user, model.

Example code:

from phi.assistant import Assistant
from phi.llm.google import Gemini

assistant = Assistant(
   llm = Gemini(model="gemini-1.5-flash"),
   add_chat_history_to_messages=True,
   debug_mode=True
)

assistant.print_response("What is 2+10?")
assistant.print_response("What if I replace 10 by 8 in previous message?")

Potential fix is at:

phidata/phi/llm/google/gemini.py

Line 50 in 6a8139b

role = "model" if msg.role == "system" else "user" if msg.role == "tool" else msg.role