code: def is_tensor_on_canonical_device(self, tensor_name):
      
      device = self.get_tensor_device(tensor_name)
      return not device or device == self.canonical_device
docs: Whether the tensor is on the first (canonical) device.
  
      Tensors not assigned to a device are assumed to be on all devices, including
      the canonical device.
  
      Args:
        tensor_name: a string, name of a tensor in the graph.
  
      Returns:
        a boolean indicating whether the tensor is on the first device.