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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 get_initial_state(self, source_length: mx.sym.Symbol, source_seq_len: int) -> AttentionState: """ Returns initial attention state. Dynamic source encoding is initialized with zeros. :param source_length: Source length. Shape: (batch_size,). :param source_seq_len: Maximum length of source sequences. """

        dynamic_source = mx.sym.reshape(mx.sym.zeros_like(source_length), shape=(-1, 1, 1))
        # dynamic_source: (batch_size, source_seq_len, num_hidden_dynamic_source)
        dynamic_source = mx.sym.broadcast_to(dynamic_source, shape=(0, source_seq_len, self.dynamic_source_num_hidden))
        return AttentionState(context=None, probs=None, dynamic_source=dynamic_source)