code: def set_void_declension(self, number_type, case_type):
          
          self.declension = []
          for i, a_number in enumerate(number_type):
              self.declension.append([])
              for _ in case_type:
                  self.declension[i].append("")
docs: >>> decl = DeclinableOneGender("armr", Gender.masculine)
          >>> decl.declension
          []
          >>> decl.set_void_declension(Number, Case)
          >>> decl.declension
          [['', '', '', ''], ['', '', '', '']]
  
          :param number_type:
          :param case_type:
          :return: