code: def to(self, unit):
          
          u = Unit("0cm")
          u.value = self.value/self.per_inch[self.unit]*self.per_inch[unit]
          u.unit = unit
          return u
docs: Convert to a given unit.
  
          Parameters
          ----------
          unit : str
             Name of the unit to convert to.
  
          Returns
          -------
          u : Unit
              new Unit object with the requested unit and computed value.