Reads atomic shells from file such as feff.inp or ATOMS file
        The lines are arranged as follows:

        x y z   ipot    Atom Symbol   Distance   Number

        with distance being the shell radius and ipot an integer identifying
        the potential used.

        Args:
            filename: File name containing atomic coord data.

        Returns:
            Atoms string.

def atoms_string_from_file(filename):
        """
        Reads atomic shells from file such as feff.inp or ATOMS file
        The lines are arranged as follows:

        x y z   ipot    Atom Symbol   Distance   Number

        with distance being the shell radius and ipot an integer identifying
        the potential used.

        Args:
            filename: File name containing atomic coord data.

        Returns:
            Atoms string.
        """
        with zopen(filename, "rt") as fobject:
            f = fobject.readlines()
            coords = 0
            atoms_str = []

            for line in f:
                if coords == 0:
                    find_atoms = line.find("ATOMS")
                    if find_atoms >= 0:
                        coords = 1
                if coords == 1 and not ("END" in line):
                    atoms_str.append(line.replace("\r", ""))

        return ''.join(atoms_str)