class_docstr: Fake variable source.
class_docstr_tok: ["Fake","variable","source","."]
code: def __init__(
      self,
      variables: Optional[types.NestedArray] = None,
      barrier: Optional[threading.Barrier] = None,
      use_default_key: bool = True,
  ):
      # Add dummy variables so we can expose them in get_variables.
      if use_default_key:
          self._variables = {
              "policy": [] if variables is None else variables
          }
      else:
          self._variables = variables
      self._barrier = barrier
  
imports: import threading
  from typing import List, Mapping, Optional, Sequence, Callable, Iterator
  from acme import core
  from acme import specs
  from acme import types
  from acme import wrappers
  import dm_env
  import numpy
  import reverb
  from rlds import rlds_types
  import tensorflow
  import tree
label_desc: Use image node_id 1 to create a new VariableSource object from inherited base classes: core with example: obj = VariableSource(variables, barrier, use_default_key)