Refactor code in contrib/rl/ folder

from deepchem.models.tensorgraph.layers import Feature, Weights, Label, Layer

import numpy as np

import tensorflow as tf

import collections

try:

  from collections.abc import Sequence as SequenceCollection

except:

  from collections import Sequence as SequenceCollection

import copy

import time

    self.n_search_episodes = n_search_episodes

    self.discount_factor = discount_factor

    self.value_weight = value_weight

    self._state_is_list = isinstance(env.state_shape[0], collections.Sequence)

    self._state_is_list = isinstance(env.state_shape[0], SequenceCollection)

    if optimizer is None:

      self._optimizer = Adam(learning_rate=0.001, beta1=0.9, beta2=0.999)

    else: