Internal helper function for getting attachments
check_args_get_attachments(msg_list, content_disposition)A list containing the full messages fetched from
the server after using fetch_full_msg.
A string indicating which type of
"Content-Disposition" attachments should be retireved. Default is
"both", which retireves regular attachments
("Content-Disposition: attachment") and inline attachments
("Content-Disposition: inline").
NULL if arguments are correct.
Other attachments helper: check_args_list_attachments,
has_attachment
Other check args: check_args_add_replace_flags,
check_args_copy_msg,
check_args_custom_search,
check_args_delete_msg,
check_args_expunge,
check_args_fetch_full_msg,
check_args_fetch_msg_header,
check_args_fetch_msg_metadata,
check_args_fetch_msg_text,
check_args_get_max_min_id,
check_args_list_attachments,
check_args_move_msg,
check_args_remove_flags,
check_args_search_date,
check_args_search_flag,
check_args_search_period,
check_args_search_size,
check_args_search_string,
check_args_search_within