code: def convert(self, value, fromunits, tounits):
          '''convert a value from one set of units to another'''
          if fromunits == tounits:
              return value
          if (fromunits,tounits) in self.unitmap:
              return value * self.unitmap[(fromunits,tounits)]
          if (tounits,fromunits) in self.unitmap:
              return value / self.unitmap[(tounits,fromunits)]
          raise fgFDMError("unknown unit mapping (%s,%s)" % (fromunits, tounits)f convert(self, value, fromunits, tounits):
          '''convert a value from one set of units to another'''
          if fromunits == tounits:
              return value
          if (fromunits,tounits) in self.unitmap:
              return value * self.unitmap[(fromunits,tounits)]
          if (tounits,fromunits) in self.unitmap:
              return value / self.unitmap[(tounits,fromunits)]
          raise fgFDMError("unknown unit mapping (%s,%s)" % (fromunits, tounits))
docs: convert a value from one set of units to another