code: private boolean isRelated(final INode source, final INode target, final char relation) {
          return relation == defautlMappings.getRelation(source, target);
      }
docs: Checks if the given source and target elements are related considering the defined relation and the temp.
  
  @param source   source
  @param target   target
  @param relation relation
  @return true if the relation holds between source and target, false otherwise.