def METHOD_NAME(self):
    """Superimpose the coordinate sets."""
    if self.coords is None or self.reference_coords is None:
        raise Exception("No coordinates set.")
    coords = self.coords
    reference_coords = self.reference_coords
    # center on centroid
    av1 = sum(coords) / self.n
    av2 = sum(reference_coords) / self.n
    coords = coords - av1
    reference_coords = reference_coords - av2
    # correlation matrix
    a = dot(transpose(coords), reference_coords)
    u, d, vt = svd(a)
    self.rot = transpose(dot(transpose(vt), transpose(u)))
    # check if we have found a reflection
    if det(self.rot) < 0:
        vt[2] = -vt[2]
        self.rot = transpose(dot(transpose(vt), transpose(u)))
    self.tran = av2 - dot(av1, self.rot)