class_docstr: Abstract class for Replay Buffer.
  
  Args:
      env_spec (EnvSpec): Environment specification.
      size_in_transitions (int): total size of transitions in the buffer
      time_horizon (int): time horizon of epsiode.
code: def _initialize_buffer(self, **kwargs):
      for key, value in kwargs.items():
          self._episode_buffer[key] = list()
          values = np.array(value)
          self._buffer[key] = np.zeros(
              [self._size, self._time_horizon, *values.shape[1:]],
              dtype=values.dtype,
          )
      self._initialized_buffer = True
  
file_path: garage/src/garage/replay_buffer/replay_buffer.py
imports: import abc
  from abc import abstractmethod
  import numpy
label_desc: Use image node_id 6 for calling the ReplayBuffer obj's underlying member method code with example usage: obj._initialize_buffer() without return types