You're seeing just the function invoke, go back to Ergo.Parser module for more information.
Link to this function

invoke(parser, ctx)

invoke/2 is the main entry point for the parsing process. It looks up the parser control function within the Context and uses it to run the given parser.

This indirection allows a different control function to be specified, e.g. by the diagnose entry point which can wrap the parser call, while still calling the same parsing function (i.e. we are not introducing debugging variants of the parsers that could be subject to different behaviours)