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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 _has_nulltype(dt):
 """ Return whether there is NullType in `dt` or not """

    if isinstance(dt, StructType):
        return any(_has_nulltype(f.dataType) for f in dt.fields)
    elif isinstance(dt, ArrayType):
        return _has_nulltype((dt.elementType))
    elif isinstance(dt, MapType):
        return _has_nulltype(dt.keyType) or _has_nulltype(dt.valueType)
    else:
        return isinstance(dt, NullType)