message: Make 'collections' a list, as documented and expected by downstream custom getters.
diff: @@ -201,7 +201,7 @@ def variable(name, shape=None, dtype=None, initializer=None,
  else [ops.GraphKeys.GLOBAL_VARIABLES])
  # Remove duplicates
  - collections = set(collections)
  + collections = list(set(collections))
  getter = variable_scope.get_variable
  if custom_getter is not None:
  getter = functools.partial(custom_getter,
  