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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def combine_first_two_dimensions(x):
 """Reshape x so that the first two dimension become one. Args: Returns: """

  ret = tf.reshape(x, tf.concat([[-1], common_layers.shape_list(x)[2:]], 0))
  old_shape = x.get_shape().dims
  a, b = old_shape[:2]
  new_shape = [a * b if a and b else None] + old_shape[2:]
  ret.set_shape(new_shape)
  return ret