Support typing.Literal as type of tool parameters or return value (#39633)

* support `typing.Literal` as type of tool parameters

* validate the `args` of `typing.Literal` roughly

* add test to get json schema for `typing.Literal` type hint

* fix: add `"type"` attribute to the parsed result of `typing.Literal`

* test: add argument `booleanish` to test multi-type literal

* style: auto fixup

tests/utils/test_chat_template_utils.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 
 import unittest
-from typing import Optional, Union
+from typing import Literal, Optional, Union
 
 from transformers.utils import DocstringParsingException, TypeHintParsingException, get_json_schema
 
@@ -384,6 +384,49 @@ class JsonSchemaGeneratorTest(unittest.TestCase):
 
         self.assertEqual(schema["function"], expected_schema)
 
+    def test_literal(self):
+        def fn(
+            temperature_format: Literal["celsius", "fahrenheit"],
+            booleanish: Literal[True, False, 0, 1, "y", "n"] = False,
+        ):
+            """
+            Test function
+
+            Args:
+                temperature_format: The temperature format to use
+                booleanish: A value that can be regarded as boolean
+
+
+            Returns:
+                The temperature
+            """
+            return -40.0
+
+        # Let's see if that gets correctly parsed as an enum
+        schema = get_json_schema(fn)
+        expected_schema = {
+            "name": "fn",
+            "description": "Test function",
+            "parameters": {
+                "type": "object",
+                "properties": {
+                    "temperature_format": {
+                        "type": "string",
+                        "enum": ["celsius", "fahrenheit"],
+                        "description": "The temperature format to use",
+                    },
+                    "booleanish": {
+                        "type": ["boolean", "integer", "string"],
+                        "enum": [True, False, 0, 1, "y", "n"],
+                        "description": "A value that can be regarded as boolean",
+                    },
+                },
+                "required": ["temperature_format"],
+            },
+        }
+
+        self.assertEqual(schema["function"], expected_schema)
+
     def test_multiline_docstring_with_types(self):
         def fn(x: int, y: int):
             """