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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 feed_forward_builder(name, hidden_dim, activation, trainable=True):
 """Get position-wise feed-forward layer builder. :param name: Prefix of names for internal layers. :param hidden_dim: Hidden dimension of feed forward layer. :param activation: Activation for feed-forward layer. :param trainable: Whether the layer is trainable. :return: """

    def _feed_forward_builder(x):
        return FeedForward(
            units=hidden_dim,
            activation=activation,
            trainable=trainable,
            name=name,
        )(x)
    return _feed_forward_builder