code: def validate(self, value):
          
          try:
              # trap blank fields here
              if value:
                  v = float(value)
                  if (v != 0 and v < self.fmin) or v > self.fmax:
                      return None
                  if abs(round(100000*v)-100000*v) > 1.e-12:
                      return None
              return value
          except ValueError:
              return None
docs: This prevents setting any value more precise than 0.00001