Function pseudo_parse_arglist 

pub fn pseudo_parse_arglist(
    arglist: &str,
    multi_line: bool,
    ctx: &PyRefContext,
    cfg: &PySigConfig,
) -> Node

Port of _pseudo_parse_arglist (_annotations.py:541-619, [PY §2.2]): comma-split fallback with [/] push/pop of desc_optional, name[:annotation][=default] partition, = always a bare desc_sig_operator (space-wrapped only when annotated), and — on total bracket imbalance — a fresh paramlist containing the raw arglist as one desc_parameter, with NO multi_line attributes (the one attr-less exception, [SIG §1.4]).

Signature note: sphinx’s version takes (signode, arglist, *, multi_line_parameter_list, trailing_comma, env); ours returns the paramlist node and reads trailing_comma from cfg / annotation context from ctx (see module docs).