Perfect the docs of copy()

theano/compile/function_module.py

@@ -559,7 +559,10 @@ class Function(object):
         Params:
             share_memory -- { boolean } Default is False. When True, two
             function share intermediate storages(storages except input and
-            output storages)
+            output storages). Otherwise two function will only share partial
+            storages( see method __copy__() ). If two functions share memory
+            and allow_gc=False, this will increase executing speed and save 
+            memory.
         ---------------------
         Returns:
             func -- Copied theano.Function