[AUR-431, AUR-435] Add Agent Interface and ReWOO Agent implementation (#31)

* add base Tool

* minor update test_tool

* update test dependency

* update test dependency

* Fix namespace conflict

* update test

* add base Agent Interface, add ReWoo Agent

* minor update

* update test

* fix typo

* remove unneeded print

* update rewoo agent

---------

Co-authored-by: trducng <trungduc1992@gmail.com>

knowledgehub/pipelines/agents/base.py

@@ -0,0 +1,67 @@
+from enum import Enum
+from typing import Dict, List, Union
+
+from pydantic import BaseModel
+
+from kotaemon.llms.chats.base import ChatLLM
+from kotaemon.llms.completions.base import LLM
+from kotaemon.pipelines.tools import BaseTool
+from kotaemon.prompt.template import PromptTemplate
+
+BaseLLM = Union[ChatLLM, LLM]
+
+
+class AgentType(Enum):
+    """
+    Enumerated type for agent types.
+    """
+
+    openai = "openai"
+    react = "react"
+    rewoo = "rewoo"
+    vanilla = "vanilla"
+    openai_memory = "openai_memory"
+
+    @staticmethod
+    def get_agent_class(_type: "AgentType"):
+        """
+        Get agent class from agent type.
+        :param _type: agent type
+        :return: agent class
+        """
+        if _type == AgentType.rewoo:
+            from .rewoo.agent import RewooAgent
+
+            return RewooAgent
+        else:
+            raise ValueError(f"Unknown agent type: {_type}")
+
+
+class AgentOutput(BaseModel):
+    """
+    Pydantic model for agent output.
+    """
+
+    output: str
+    cost: float
+    token_usage: int
+
+
+class BaseAgent(BaseTool):
+    name: str
+    """Name of the agent."""
+    type: AgentType
+    """Agent type, must be one of AgentType"""
+    description: str
+    """Description used to tell the model how/when/why to use the agent.
+    You can provide few-shot examples as a part of the description. This will be
+    input to the prompt of LLM."""
+    llm: Union[BaseLLM, Dict[str, BaseLLM]]
+    """Specify LLM to be used in the model, cam be a dict to supply different
+    LLMs to multiple purposes in the agent"""
+    prompt_template: Union[PromptTemplate, Dict[str, PromptTemplate]]
+    """A prompt template or a dict to supply different prompt to the agent
+    """
+    plugins: List[BaseTool]
+    """List of plugins / tools to be used in the agent
+    """