def make_chimera_command_file(filename, content='',
    color_secondary_structure=True):
    """
    Creates a Chimera command file for protein structure visualisation.

    :param str filename: path to mmcif file
    :param content: personalised content of the chimera command file
    :type content: str or iterable
    :param bool color_secondary_structure: wheter to append secondary structure coloring
    :return str: lines to be written to file

    .. todo:: Select models, chains, residues and select atoms:
        display #{model_n}:{start}-{stop}.{chain}@ca

    """
    line = 'open {filename}\n'.format(filename=filename)
    if isinstance(content, str):
        line += content
    elif hasattr(content, '__iter__'):
        line += '\n'.join(content)
    if color_secondary_structure:
        line += (
            'color green,r helix\ncolor yellow,r strand\ncolor gray,r coil\n')
    return line
