+/**
+ *
+ *
+ * the command line parser of the writer
+ *
+ * It should check whether the command line options given by \a options are
+ * valid. On success, it should return a pointer to the writer-specific
+ * configuration data determined by \a options. Note that this might be called
+ * more than once with different values of \a options.
+ *
+ */
+ void * (*parse_config)(char *options);