On https://www.klayout.de/doc/about/drc_ref_source.html
page as a whole, enumerates argument signatures using "layer_into" several times like:
source.input(layer_into)
Text does not mention/explain layer_into but mentions LayerInfo as in:
... The layer can be specified by layer and optionally datatype, by a LayerInfo object or ...
Are those layer_into typos for layer_info (else what does it mean)?