Create a supercell.

        Args:
            scaling_matrix: A scaling matrix for transforming the lattice
                vectors. Has to be all integers. Several options are possible:

                a. A full 3x3 scaling matrix defining the linear combination
                   the old lattice vectors. E.g., [[2,1,0],[0,3,0],[0,0,
                   1]] generates a new structure with lattice vectors a' =
                   2a + b, b' = 3b, c' = c where a, b, and c are the lattice
                   vectors of the original structure.
                b. An sequence of three scaling factors. E.g., [2, 1, 1]
                   specifies that the supercell should have dimensions 2a x b x
                   c.
                c. A number, which simply scales all lattice vectors by the
                   same factor.
            to_unit_cell: Whether or not to fall back sites into the unit cell

def make_supercell(self, scaling_matrix, to_unit_cell=True):
        """
        Create a supercell.

        Args:
            scaling_matrix: A scaling matrix for transforming the lattice
                vectors. Has to be all integers. Several options are possible:

                a. A full 3x3 scaling matrix defining the linear combination
                   the old lattice vectors. E.g., [[2,1,0],[0,3,0],[0,0,
                   1]] generates a new structure with lattice vectors a' =
                   2a + b, b' = 3b, c' = c where a, b, and c are the lattice
                   vectors of the original structure.
                b. An sequence of three scaling factors. E.g., [2, 1, 1]
                   specifies that the supercell should have dimensions 2a x b x
                   c.
                c. A number, which simply scales all lattice vectors by the
                   same factor.
            to_unit_cell: Whether or not to fall back sites into the unit cell
        """
        s = self * scaling_matrix
        if to_unit_cell:
            for site in s:
                site.to_unit_cell(in_place=True)
        self._sites = s.sites
        self._lattice = s.lattice