Return the cartesian coordinates of the molecule

def get_cart_coords(self):
        """
        Return the cartesian coordinates of the molecule
        """
        def to_s(x):
            return "%0.6f" % x

        outs = []
        for i, site in enumerate(self._mol):
            outs.append(" ".join([site.species_string,
                                  " ".join([to_s(j) for j in site.coords])]))
        return "\n".join(outs)