def METHOD_NAME(filename, atoms):
    """Write FHI-aims geometry files in phonopy context."""
    lines = ""
    lines += "# geometry.in for FHI-aims \n"
    lines += "# | generated by phonopy.FHIaims.write_aims() \n"
    lattice_vector_line = "lattice_vector " + "%16.16f " * 3 + "\n"
    for vec in atoms.get_cell():
        lines += lattice_vector_line % tuple(vec)
    N = atoms.get_number_of_atoms()
    atom_line = "atom " + "%16.16f " * 3 + "%s \n"
    positions = atoms.get_positions()
    symbols = atoms.get_chemical_symbols()
    initial_moment_line = "initial_moment %16.6f\n"
    magmoms = atoms.get_magnetic_moments()
    for n in range(N):
        lines += atom_line % (tuple(positions[n]) + (symbols[n],))
        if magmoms is not None:
            lines += initial_moment_line % magmoms[n]
    with open(filename, "w") as f:
        f.write(lines)