code: def copy(self, nominal=None, uncertainties=None):
          
          if nominal is None:
              nominal = self.nominal
          if uncertainties is None:
              uncertainties = self.uncertainties
          return self.__class__(nominal, uncertainties=uncertainties)
docs: Returns a deep copy of the number instance. When *nominal* or *uncertainties* are set, they
          overwrite the fields of the copied instance.