Get element projected Dos.

        Returns:
            dict of {Element: Dos}

def get_element_dos(self):
        """
        Get element projected Dos.

        Returns:
            dict of {Element: Dos}
        """

        el_dos = {}
        for site, atom_dos in self.pdos.items():
            el = site.specie
            if el not in el_dos:
                el_dos[el] = np.array(atom_dos)
            else:
                el_dos[el] += np.array(atom_dos)
        return {el: PhononDos(self.frequencies, densities)
                for el, densities in el_dos.items()}