Add support to declare imports for code agent (#31355)

* Support import declaration in Code Agent

tests/agents/test_agents.py

@@ -141,15 +141,21 @@ Action:
     def test_init_agent_with_different_toolsets(self):
         toolset_1 = []
         agent = ReactCodeAgent(tools=toolset_1, llm_engine=fake_react_code_llm)
-        assert len(agent.toolbox.tools) == 1  # contains only final_answer tool
+        assert (
+            len(agent.toolbox.tools) == 1
+        )  # when no tools are provided, only the final_answer tool is added by default
 
         toolset_2 = [PythonInterpreterTool(), PythonInterpreterTool()]
         agent = ReactCodeAgent(tools=toolset_2, llm_engine=fake_react_code_llm)
-        assert len(agent.toolbox.tools) == 2  # added final_answer tool
+        assert (
+            len(agent.toolbox.tools) == 2
+        )  # deduplication of tools, so only one python_interpreter tool is added in addition to final_answer
 
         toolset_3 = Toolbox(toolset_2)
         agent = ReactCodeAgent(tools=toolset_3, llm_engine=fake_react_code_llm)
-        assert len(agent.toolbox.tools) == 2  # added final_answer tool
+        assert (
+            len(agent.toolbox.tools) == 2
+        )  # same as previous one, where toolset_3 is an instantiation of previous one
 
         # check that add_base_tools will not interfere with existing tools
         with pytest.raises(KeyError) as e: