class_docstr: Base wrapper class.
class_docstr_tok: ["Base","wrapper","class","."]
docstr: Number of combined environments.
docstr_tok: ["Number","of","combined","environments","."]
code: def __len__(self):
      """Number of combined environments."""
      return self._length
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from six.moves import range
  from tensor2tensor.rl.envs.in_graph_batch_env import InGraphBatchEnv
  import tensorflow.compat.v1
label_desc: Use image node_id 5 for calling the WrapperBase obj's underlying member method code with example usage: obj.__len__() and returns: self