class_docstr: ABC for loss functions of each head. Child class must implement input_schema() and loss_forward()
class_docstr_tok: ["ABC","for","loss","functions","of","each","head",".","Child","class","must","implement","input_schema","(",")","and","loss_forward","(",")"]
docstr: :return: schema for input of hybrid_forward. Read docstring for LossInputSchema for details.
docstr_tok: [":","return",":","schema","for","input","of","hybrid_forward",".","Read","docstring","for","LossInputSchema","for","details","."]
code: def input_schema(self) -> LossInputSchema:
      """
      :return: schema for input of hybrid_forward. Read docstring for LossInputSchema for details.
      """
      raise NotImplementedError
  
imports: from typing import Dict, List, Union, Tuple
  import mxnet
  from mxnet.initializer import Initializer, register
  from mxnet.gluon import nn, loss
  from mxnet.ndarray import NDArray
  from mxnet.symbol import Symbol
  from rl_coach.base_parameters import AgentParameters
  from rl_coach.spaces import SpacesDefinition
label_desc: Use image node_id 2 for calling the HeadLoss obj's underlying member method code with example usage: obj.input_schema() without return types