Replace tf.contrib.distributions with tensorflow_probability.distributions

[b-sia]

Tensorflow2 no longer supports the contrib module. Could we replace tf.contrib.distributions with tensorflow_probability.distributions?

agents/scripts/network.py

# Copyright 2017 The TensorFlow Agents Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Policy networks for agents."""

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import functools
import operator

import gym
import numpy as np
import tensorflow as tf
from tensorflow_probability import distributions

import agents

tfd = distributions