code: def to_base_units(self):
          
          # Convert to "standard" units, as defined by the conversions dict above
          amount = self.value
  
          numer_factor, numer_units = convert_units_to_base_units(self.unit_numer)
          denom_factor, denom_units = convert_units_to_base_units(self.unit_denom)
  
          return Number(
              amount * numer_factor / denom_factor,
              unit_numer=numer_units,
              unit_denom=denom_units,
          )
docs: Convert to a fixed set of "base" units.  The particular units are
          arbitrary; what's important is that they're consistent.
  
          Used for addition and comparisons.