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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_index_from_alias(alias_name, index_client=None):
 """Retrieve the base index name from an alias Args: alias_name (str) Name of the alias index_client (Elasticsearch.IndicesClient) an Elasticsearch index client. Optional, will create one if not given Returns: (str) Name of index """

    index_client = index_client or indices_client()
    if not index_client.exists_alias(name=alias_name):
        return None
    return list(index_client.get_alias(name=alias_name).keys())[0]