def METHOD_NAME(self, dtypes: Dict[str, Any]) -> Dict[str, Any]:
    json_schema = self._default_json_schema
    for key, val in dtypes.items():
        if val == "int64":
            json_schema["properties"][key] = {"type": ["null", "integer"]}
        elif val == "float64":
            json_schema["properties"][key] = {"type": ["null", "number"]}
        elif val == "bool":
            json_schema["properties"][key] = {"type": ["null", "boolean"]}
        # Special case for last_modified timestamp
        elif key == "last_modified":
            json_schema["properties"][key] = {"type": ["null", "string"], "format": "date-time"}
        # Default to string
        else:
            json_schema["properties"][key] = {"type": ["null", "string"]}
    return json_schema