code: def copy(self, newdata=None):
          '''Return a copy of the cube with optionally new data.'''
          if newdata is None:
              newdata = self.data.copy()
          return self.__class__(
              self.molecule, self.origin.copy(), self.axes.copy(),
              self.nrep.copy(), newdata, self.subtitle, self.nuclear_charges
          f copy(self, newdata=None):
          '''Return a copy of the cube with optionally new data.'''
          if newdata is None:
              newdata = self.data.copy()
          return self.__class__(
              self.molecule, self.origin.copy(), self.axes.copy(),
              self.nrep.copy(), newdata, self.subtitle, self.nuclear_charges
          )
docs: Return a copy of the cube with optionally new data.