code: def input_schema(self) -> LossInputSchema:
      return LossInputSchema(
          head_outputs=["new_policy_values"],
          agent_inputs=["old_policy_values"],
          targets=["target_values"],
      )
  
file_path: coach/rl_coach/architectures/mxnet_components/heads/ppo_v_head.py
imports: from typing import List, Tuple, Union
  from types import ModuleType
  import mxnet
  from mxnet.gluon import nn
  from rl_coach.architectures.mxnet_components.heads.head import Head, HeadLoss, LossInputSchema, NormalizedRSSInitializer
  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 ActionProbabilities
  from rl_coach.spaces import SpacesDefinition
label_desc: Use image node_id 2 for calling the PPOVHeadLoss obj's underlying member method code with example usage: obj.input_schema() and returns: LossInputSchema