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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 nonfirst_authors(self, key, value):
 """Populate ``700`` MARC field. Also populates the ``701`` MARC field through side-effects. """

    field_700 = self.get('700__', [])
    field_701 = self.get('701__', [])

    is_supervisor = any(el.lower().startswith('dir') for el in force_list(value.get('e', '')))
    if is_supervisor:
        field_701.append(_converted_author(value))
    else:
        field_700.append(_converted_author(value))

    self['701__'] = field_701
    return field_700