def _includes(opt):
    """
    Return the #include directives for the user-defined list of include files.
    """
    includes = []
    if opt.include_files is not None and len(opt.include_files) > 0:
        for include_file in opt.include_files:
            if include_file[0] == '"' or include_file[0] == '<':
                includes.append('#include {0}'.format(include_file))
            else:
                includes.append('#include "{0}"'.format(include_file))
    return includes
