Function write_pslf 

pub fn write_pslf(net: &Network) -> Conversion

Serialize net to PSLF .epc text.

The inverse of the reader’s column layout: it emits the same colon separated lhs : rhs records, so a .epc -> Network -> .epc round trip preserves the power flow core. Where a PSLF read stashed a field the neutral model does not name under a pslf_* extras key (the ZIP load split, the per unit shunt G/B, the branch circuit id, the transformer winding base), the writer replays it; otherwise it synthesizes the column. Same-format byte-exact echo rides the retained source (see crate::write_as); this is the cross-format path and the fallback when the source text was dropped (e.g. after a JSON round trip).