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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_na_values(col, na_values, na_fvalues, keep_default_na):
 """ Get the NaN values for a given column. Parameters col : str The name of the column. na_values : array-like, dict The object listing the NaN values as strings. na_fvalues : array-like, dict The object listing the NaN values as floats. keep_default_na : bool If `na_values` is a dict, and the column is not mapped in the dictionary, whether to return the default NaN values or the empty set. Returns ------- nan_tuple : A length-two tuple composed of 1) na_values : the string NaN values for that column. 2) na_fvalues : the float NaN values for that column. """


    if isinstance(na_values, dict):
        if col in na_values:
            return na_values[col], na_fvalues[col]
        else:
            if keep_default_na:
                return _NA_VALUES, set()

            return set(), set()
    else:
        return na_values, na_fvalues