How to use self defined variable in an Agent?
This issue may sound silly, I apologize for not being able to find the answer (and for my poor English).

For example, I want my chatbot only use paths from a list I give. I tried to include the following content in suffix:
```py
"""
omit...
You should only use the following file paths:
{path_list}
omit...
"""
```

But how can I add `path_list` to `input_variables`? I noticed that the `create_prompt` method has the following statement:
```py
if input_variables is None:
    input_variables = ["input", "chat_history", "agent_scratchpad"]
```

So I tried adding `input_variables` in `agent_kwargs`:
```py
agent = initialize_agent(
    tools,
    llm,
    agent="conversational-react-description",
    verbose=True,
    memory=memory,
    return_intermediate_steps=True,
    agent_kwargs={
        'prefix': CHAT_BOT_PREFIX,
        'format_instructions': CHAT_BOT_FORMAT_INSTRUCTIONS,
        'suffix': CHAT_BOT_SUFFIX,
        'input_variables': ["input", "chat_history", "agent_scratchpad", "path_list"], # here
    },
)
```

This does create a prompt in the agent with a `path_list` variable in it. But how can I pass the value of path_list?

The way I thought was to pass it togethor with `input`.
```py
result = agent({"input": str_input, "path_list": path_list_str})
```

But this doesn't work. It raises the following error:
```text
ValueError: One input key expected got ['path_list', 'input']
```

I don't know if there's another way or if I'm missing something.