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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 compress_self_attention_layer(x, hparams, name=None):
 """Attend function."""

  with tf.variable_scope(name, default_name="compress_self_attention"):
    x, xshape, _ = cia.maybe_reshape_4d_to_3d(x)
    y = common_attention.multihead_attention(
        common_layers.layer_preprocess(x, hparams),
        None,
        None,
        hparams.attention_key_channels or hparams.hidden_size,
        hparams.attention_value_channels or hparams.hidden_size,
        hparams.hidden_size, hparams.num_heads,
        hparams.attention_dropout)
    res = common_layers.layer_postprocess(x, y, hparams)
    return tf.reshape(res, xshape)