code: public boolean isMatch(Endpoint other) {
          assert isMarker() : "isMatch can only be used on marker end-points";
  
          // Same structure as compareTo, except that nulls 'match' IDs (not <)
          int ans = 0;
  
          // A null edgeLabel implies that all endpoints of that vertex must be
          // matched
          if (edgeLabel == null) {
              return true;
          }
  
          if (other.getEdgeLabel() == null) {
              // This is not a match because the existing Endpoint no label, but
              // the marker does
              return false;
          }
  
          ans = edgeLabel.compareTo(other.getEdgeLabel());
          if (ans != 0) {
              return false;
          }
  
          // A null edgeId implies the 'first' edge for the given vertex for the
          // given edgeLabel
          if (edgeId == null) {
              return true;
          }
  
          return (edgeId.compareTo(other.getEdgeId()) == 0);
      }
docs: This method must only be called on marker endpoints, i.e., end-points
  used for matching existing Endpoints in the B-Tree. It returns true if
  the given Endpoint matches this marker