docstr: Used for forward pass through middleware network.
  
  :param F: backend api, either `mxnet.nd` or `mxnet.sym` (if block has been hybridized).
  :param x: state embedding, of shape (batch_size, in_channels).
  :return: state middleware embedding, where shape is (batch_size, channels).
code: def hybrid_forward(
      self, F: ModuleType, x: nd_sym_type, *args, **kwargs
  ) -> nd_sym_type:
      """
      Used for forward pass through middleware network.
  
      :param F: backend api, either `mxnet.nd` or `mxnet.sym` (if block has been hybridized).
      :param x: state embedding, of shape (batch_size, in_channels).
      :return: state middleware embedding, where shape is (batch_size, channels).
      """
      return self.net(x)
  
file_path: coach/rl_coach/architectures/mxnet_components/middlewares/middleware.py
imports: from typing import Union
  from types import ModuleType
  import mxnet
  from mxnet.gluon import nn
  from rl_coach.architectures.middleware_parameters import MiddlewareParameters
  from rl_coach.architectures.mxnet_components.layers import convert_layer
  from rl_coach.base_parameters import MiddlewareScheme
label_desc: Use image node_id 3 for calling the Middleware obj's underlying member method code with example usage: obj.hybrid_forward(F, x) and returns: self