code: def convert_unit(number, input_unit, expected_unit):
      
      for mapping in unit_mapping:
          if input_unit == mapping[0] and expected_unit == mapping[1]:
              return number * mapping[2]
          if input_unit == mapping[1] and expected_unit == mapping[0]:
              return number / mapping[2]
  
      return None
docs: A helper to convert the unit.
  
      :param number: The number to update.
      :type number: int
  
      :param input_unit: The unit of the number.
      :type input_unit: safe.definitions.units
  
      :param expected_unit: The expected output unit.
      :type expected_unit: safe.definitions.units
  
      :return: The new number in the expected unit.
      :rtype: int