Set if the nature of the format or configuration does not allow (much)
parsing, and the parser should operate in passthrough mode (which only
applies when operating in push mode). That is, incoming buffers are
pushed through unmodified, i.e. no @check_valid_frame or @parse_frame
callbacks will be invoked, but @pre_push_frame will still be invoked,
so subclass can perform as much or as little is appropriate for
passthrough semantics in @pre_push_frame.
Set if the nature of the format or configuration does not allow (much) parsing, and the parser should operate in passthrough mode (which only applies when operating in push mode). That is, incoming buffers are pushed through unmodified, i.e. no @check_valid_frame or @parse_frame callbacks will be invoked, but @pre_push_frame will still be invoked, so subclass can perform as much or as little is appropriate for passthrough semantics in @pre_push_frame.