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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_national_number_groups(numobj, formatting_pattern):
 """Helper method to get the national-number part of a number, formatted without any national prefix, and return it as a set of digit blocks that should be formatted together according to the formatting pattern passed in."""

    # If a format is provided, we format the NSN only, and split that according to the separator.
    nsn = national_significant_number(numobj)
    return _format_nsn_using_pattern(nsn, formatting_pattern,
                                     PhoneNumberFormat.RFC3966).split(U_DASH)