def __mul__(self, repeat):
result = Graph.__mul__(self, repeat)
result.__class__ = MolecularGraph
# copy numbers
numbers = numpy.zeros((repeat, len(self.numbers)), int)
numbers[:] = self.numbers
result._numbers = numbers.ravel()
result._numbers.setflags(write=False)
# copy orders
orders = numpy.zeros((repeat, len(self.orders)), int)
orders[:] = self.orders
result._orders = orders.ravel()
result._orders.setflags(write=False)
return result
