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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 relations_for_id(relid=None):
 """Get relations of a specific relation ID"""

    relation_data = []
    relid = relid or relation_ids()
    for unit in related_units(relid):
        unit_data = relation_for_unit(unit, relid)
        unit_data['__relid__'] = relid
        relation_data.append(unit_data)
    return relation_data