Replace collections.abc.Mapping with typing.Mapping.
This should fix an error where the typing object was not subscriptable and
was causing pytype to fail.
"""Functions for making TensorFlow datasets for sampling from Reverb replay."""
import collections
-from collections.abc import Mapping
import os
-from typing import Callable, Optional, Union
+from typing import Callable, Mapping, Optional, Union
from acme import specs
from acme import types
