Excluding properties with defaults from required as per issue #41 (#74)

openai_function_call/function_calls.py

@@ -72,8 +72,9 @@ class openai_function:
             if k not in ("v__duplicate_kwargs", "args", "kwargs")
         }
         parameters["required"] = sorted(
-            parameters["properties"]
-        )  # bug workaround see lc
+            k for k, v in parameters["properties"].items() 
+            if not "default" in v
+        )
         _remove_a_key(parameters, "additionalProperties")
         self.openai_schema = {
             "name": self.func.__name__,
@@ -130,7 +131,10 @@ class OpenAISchema(BaseModel):
         parameters = {
             k: v for k, v in schema.items() if k not in ("title", "description")
         }
-        parameters["required"] = sorted(parameters["properties"])
+        parameters["required"] = sorted(
+            k for k, v in parameters["properties"].items() 
+            if not "default" in v
+        )
 
         if "description" not in schema:
             schema[