code: def add_implicit_resolver(tag, regexp, first=None,
          Loader=Loader, Dumper=Dumper):
      
      Loader.add_implicit_resolver(tag, regexp, first)
      Dumper.add_implicit_resolver(tag, regexp, first)
docs: Add an implicit scalar detector.
      If an implicit scalar value matches the given regexp,
      the corresponding tag is assigned to the scalar.
      first is a sequence of possible initial characters or None.