docs: def addResource(self, pid):
          """Add a resource to the Resource Map.
  
          Args:
            pid : str
  
          """
          self._check_initialized()
          try:
              # is entry already in place?
              self.getObjectByPid(pid)
              return
          except IndexError:
              pass
          # Entry not present, add it to the graph
          oid = self._pid_to_id(pid)
          obj = rdflib.URIRef(oid)
          ag = self.getAggregation()
          self.add((ag, ORE.aggregates, obj))
          self.add((obj, ORE.isAggregatedBy, ag))
          self.add((obj, DCTERMS.identifier, rdflib.term.Literal(pid)))