code: def get_input_layers(layer: Layer) -> set[Layer]:
      """Returns all layers that created this layer's inputs."""
      ret = set()
  
      for node_index in range(len(layer._inbound_nodes)):
          Xs = ibackend.to_list(layer.get_input_at(node_index))
          for X in Xs:
              ret.add(X._keras_history[0])
  
      return ret
  
imports: from __future__ import annotations
  import tensorflow.keras.layers
  from tensorflow import Module, keras
  import innvestigate.backend
  from innvestigate.backend.types import Layer, Model
label_desc: Use image node_id 15 for calling a global function with example usage: get_input_layers(layer) and returns: ret