code: def input_schema(self) -> LossInputSchema:
      return LossInputSchema(
          head_outputs=["pred"], agent_inputs=[], targets=["target"]
      )
  
file_path: coach/rl_coach/architectures/mxnet_components/heads/q_head.py
imports: from typing import Union, List, Tuple
  from types import ModuleType
  import mxnet
  from mxnet.gluon.loss import Loss, HuberLoss, L2Loss
  from mxnet.gluon import nn
  from rl_coach.architectures.mxnet_components.heads.head import Head, HeadLoss, LossInputSchema
  from rl_coach.architectures.mxnet_components.heads.head import LOSS_OUT_TYPE_LOSS
  from rl_coach.base_parameters import AgentParameters
  from rl_coach.core_types import QActionStateValue
  from rl_coach.spaces import SpacesDefinition, BoxActionSpace, DiscreteActionSpace
label_desc: Use image node_id 2 for calling the QHeadLoss obj's underlying member method code with example usage: obj.input_schema() and returns: LossInputSchema