code: def expand_batch_coordinates(bc, length_factor):
    
    assert bc.get_shape().as_list() == [1, None, 1]
    # bc has shape [1, length, 1]
    bc *= tf.constant([[1] * length_factor])
    # bc has shape [1, length, length_factor]
    bc = tf.reshape(bc, [1, -1, 1])
    # bc has shape [1, length*length_factor]
    return bc
docs: Duplicate elements of bc by length_factor.
  
    Args:
      bc (tf.Tensor): int32 tensor of shape [1, length, 1]
      length_factor (int):
  
    Returns:
      tf.Tensor: of shape [1, length*length_factor, 1] where every elements has
        been duplicated length_factor times.