def to_cartesian(self, fractional):
return np.dot(fractional, self.matrix.transpose())<EOL>
Converts fractional to Cartesian coordinates

           Argument:
            | ``fractional``  --  Can be a numpy array with shape (3, ) or with shape
                                  (N, 3).

           The return value has the same shape as the argument. This function is
           the inverse of to_fractional.