Refactor agents and tools (#91)

* Move tools to agents

* Move agents to dedicate place

* Remove subclassing BaseAgent from BaseTool

knowledgehub/agents/tools/google.py

@@ -0,0 +1,51 @@
+from typing import AnyStr, Optional, Type
+
+from langchain.utilities import SerpAPIWrapper
+from pydantic import BaseModel, Field
+
+from .base import BaseTool
+
+
+class GoogleSearchArgs(BaseModel):
+    query: str = Field(..., description="a search query")
+
+
+class GoogleSearchTool(BaseTool):
+    name = "google_search"
+    description = (
+        "A search engine retrieving top search results as snippets from Google. "
+        "Input should be a search query."
+    )
+    args_schema: Optional[Type[BaseModel]] = GoogleSearchArgs
+
+    def _run_tool(self, query: AnyStr) -> str:
+        try:
+            from googlesearch import search
+        except ImportError:
+            raise ImportError(
+                "install googlesearch using `pip3 install googlesearch-python` to "
+                "use this tool"
+            )
+        output = ""
+        search_results = search(query, advanced=True)
+        if search_results:
+            output = "\n".join(
+                "{} {}".format(item.title, item.description) for item in search_results
+            )
+
+        return output
+
+
+class SerpTool(BaseTool):
+    name = "google_search"
+    description = (
+        "Worker that searches results from Google. Useful when you need to find short "
+        "and succinct answers about a specific topic. Input should be a search query."
+    )
+    args_schema: Optional[Type[BaseModel]] = GoogleSearchArgs
+
+    def _run_tool(self, query: AnyStr) -> str:
+        tool = SerpAPIWrapper()
+        evidence = tool.run(query)
+
+        return evidence