code: def test_get_source_inputs(self):
      x1 = backend.KerasTensor(shape=(2,))
      x2 = backend.KerasTensor(shape=(2,))
      x = x1 + x2
      x += 2
      x = ops.square(x)
      self.assertEqual(operation_utils.get_source_inputs(x), [x1, x2])
  
imports: from keras import backend
  from keras import ops
  from keras import testing
  from keras.layers.core import input_layer
  from keras.ops import operation_utils
label_desc: Use image node_id 1 for calling the OperationUtilsTest obj's underlying member method code with example usage: obj.test_get_source_inputs() without return types