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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 add_children(d, key, **kwarg):
 """Add a children with key and attributes. If children already EXISTS, OVERWRITE it. Usage:: {'_meta': {'population': 27800000, '_rootname': 'US'}, 'MD': {'_meta': {'name': 'maryland', 'population': 200000}}, 'VA': {'_meta': {'name': 'virginia', 'population': 100000}}} name="arlington county", population=5000) name="vienna county", population=5000) name="montgomery country", population=5800) name="fredrick country", population=1400) name="RiverHouse 1400", population=437) name="Crystal plaza South", population=681) name="loft hotel", population=216) {'MD': {'_meta': {'name': 'maryland', 'population': 200000}, 'bethesta': {'_meta': {'name': 'montgomery country', 'population': 5800}}, 'germentown': {'_meta': {'name': 'fredrick country', 'population': 1400}}}, 'VA': {'_meta': {'name': 'virginia', 'population': 100000}, 'arlington': {'_meta': {'name': 'arlington county', 'population': 5000}, 'crystal plaza': {'_meta': {'name': 'Crystal plaza South', 'population': 681}}, 'loft': {'_meta': {'name': 'loft hotel', 'population': 216}}, 'riverhouse': {'_meta': {'name': 'RiverHouse 1400', 'population': 437}}}, 'vienna': {'_meta': {'name': 'vienna county', 'population': 1500}}}, '_meta': {'_rootname': 'US', 'population': 27800000.0}} """

        if kwarg:
            d[key] = {_meta: kwarg}
        else:
            d[key] = dict()