def skip_header(cube_file):
    """Moves cube file to first density line.

    Parameters
    ----------
    cube_file : `io.textiowrapper`
        Opened file variable.
    
    Returns
    -------
    `io.textiowrapper`
        File object with header info skipped and ready to read first density
        line.
    """

    # Skips two comment lines
    next(cube_file)
    next(cube_file)

    # Skips box and atom information
    atom_num, _, _, _ = cube_file.readline().split()
    for i in range(0, 3 + int(atom_num)):
        next(cube_file)

    return cube_file