<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def combine_last_two_dimensions(x):
 """Reshape x so that the last two dimension become one. Args: Returns: """

  x_shape = common_layers.shape_list(x)
  a, b = x_shape[-2:]
  return tf.reshape(x, x_shape[:-2] + [a * b])