Move function/actor exporting & loading code to function_manager.py (#3003)

Move function/actor exporting & loading code to function_manager.py to prepare the code change for function descriptor for python.

python/ray/utils.py

@@ -5,6 +5,7 @@ from __future__ import print_function
 import binascii
 import functools
 import hashlib
+import inspect
 import numpy as np
 import os
 import subprocess
@@ -144,6 +145,23 @@ def is_cython(obj):
         (hasattr(obj, "__func__") and check_cython(obj.__func__))
 
 
+def is_function_or_method(obj):
+    """Check if an object is a function or method.
+
+    Args:
+        obj: The Python object in question.
+
+    Returns:
+        True if the object is an function or method.
+    """
+    return (inspect.isfunction(obj) or inspect.ismethod(obj) or is_cython(obj))
+
+
+def is_class_method(f):
+    """Returns whether the given method is a class_method."""
+    return hasattr(f, "__self__") and f.__self__ is not None
+
+
 def random_string():
     """Generate a random string to use as an ID.