code: def find_object(self, key, layers):
          '''find an object to be modified'''
          state = self.state
  
          if layers is None or layers == '':
              layers = state.layers.keys()
          for layer in layers:
              if key in state.layers[layer]:
                  return state.layers[layer][key]
          return Nonf find_object(self, key, layers):
          '''find an object to be modified'''
          state = self.state
  
          if layers is None or layers == '':
              layers = state.layers.keys()
          for layer in layers:
              if key in state.layers[layer]:
                  return state.layers[layer][key]
          return None
docs: find an object to be modified