docstr: Updates value of a variable.
  :param assign_op: a callable assign function for setting the variable
  :param value: a value to set the variable to
  :param placeholder: unused (placeholder in symbolic framework backends)
docstr_tok: ["Updates","value","of","a","variable",".",":","param","assign_op",":","a","callable","assign","function","for","setting","the","variable",":","param","value",":","a","value","to","set","the","variable","to",":","param","placeholder",":","unused","(","placeholder","in","symbolic","framework","backends",")"]
code: def set_variable_value(
      self, assign_op: callable, value: Any, placeholder=None
  ) -> None:
      """
      Updates value of a variable.
      :param assign_op: a callable assign function for setting the variable
      :param value: a value to set the variable to
      :param placeholder: unused (placeholder in symbolic framework backends)
      """
      assert callable(assign_op)
      assign_op(value)
  
imports: import copy
  from typing import Any, Dict, Generator, List, Tuple, Union
  import numpy
  import mxnet
  from mxnet import autograd, gluon, nd
  from mxnet.ndarray import NDArray
  from rl_coach.architectures.architecture import Architecture
  from rl_coach.architectures.mxnet_components.heads.head import LOSS_OUT_TYPE_LOSS, LOSS_OUT_TYPE_REGULARIZATION
  from rl_coach.architectures.mxnet_components import utils
  from rl_coach.architectures.mxnet_components.savers import ParameterDictSaver, OnnxSaver
  from rl_coach.base_parameters import AgentParameters
  from rl_coach.logger import screen
  from rl_coach.saver import SaverCollection
  from rl_coach.spaces import SpacesDefinition
  from rl_coach.utils import force_list, squeeze_list
label_desc: Use image node_id 20 for calling the MxnetArchitecture obj's underlying member method code with example usage: obj.set_variable_value(assign_op, value, placeholder) without return types