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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 namedb_get_name_from_name_hash128( cur, name_hash128, block_number ):
 """ Given the hexlified 128-bit hash of a name, get the name. """


    unexpired_query, unexpired_args = namedb_select_where_unexpired_names( block_number )

    select_query = "SELECT name FROM name_records JOIN namespaces ON name_records.namespace_id = namespaces.namespace_id " + \
                   "WHERE name_hash128 = ? AND revoked = 0 AND " + unexpired_query + ";"

    args = (name_hash128,) + unexpired_args
    name_rows = namedb_query_execute( cur, select_query, args )

    name_row = name_rows.fetchone()
    if name_row is None:
        # no such namespace 
        return None 

    return name_row['name']