enum is not supported in array for function_declarations in convert_to_genai_function_declarations

[taoxinyi]

The following code output doesn't contain enum field in array items field, which is supported in gemini

from typing import List

from langchain_core.tools import tool
from langchain_core.utils.function_calling import convert_to_openai_tool
from langchain_google_genai._function_utils import convert_to_genai_function_declarations


class Color(Enum):
    RED="RED"
    GREEN="GREEN"
    YELLOW="YELLOW"


@tool
def describe_colors(colors:List[Color]) -> str:
   """ describe colors """
   return "\n".join(colors)
print(convert_to_openai_tool(describe_colors))
print(convert_to_genai_function_declarations([describe_colors]))

output:

{'type': 'function', 'function': {'name': 'describe_colors', 'description': 'describe colors', 'parameters': {'properties': {'colors': {'items': {'enum': ['RED', 'GREEN', 'YELLOW'], 'type': 'string'}, 'type': 'array'}}, 'required': ['colors'], 'type': 'object'}}}
function_declarations {
  name: "describe_colors"
  description: "describe colors"
  parameters {
    type_: OBJECT
    description: "describe colors "
    properties {
      key: "colors"
      value {
        type_: ARRAY
        items {
          type_: STRING
          description: "Color"
        }
      }
    }
    required: "colors"
  }
}

expected:
enum fields in items field

[rsinger86]

I'm running into the same problem