docs: def _build_xrefs(self):
          '''
          Internal function to populate the xrefs list with the external
          references to be used in searching plugins and potentially
          other functions as well.
          '''
          xrefs = set()
  
          plugins = self.plugins()
          for plugin in plugins:
              for xref in plugin['xrefs'].split(', '):
                  xrf = xref.replace('-', '_').split(':')[0]
                  if xrf is not '':
                      xrefs.add(xrf)
          self._xrefs = list(xrefs)