code: private boolean validOrthologousStatement(final Statement stmt) {
          // test statement is well-formed
          if (stmt.getRelationshipType() == RelationshipType.ORTHOLOGOUS
                  && stmt.getObject() != null
                  && stmt.getObject().getTerm() != null) {
  
              // test subject has only one namespace parameter
              final Term subject = stmt.getSubject();
              List<Parameter> subparams = subject.getParameters();
              if (subparams == null || subparams.size() != 1
                      || subparams.get(0).getNamespace() == null) {
                  return false;
              }
  
              // test object has only one namespace parameter
              final Term object = stmt.getObject().getTerm();
              List<Parameter> objparams = object.getParameters();
              if (objparams == null || objparams.size() != 1
                      || objparams.get(0).getNamespace() == null) {
                  return false;
              }
  
              return true;
          }
  
          return false;
      }
docs: Determines whether the {@link Statement statement} is a valid
  {@link RelationshipType#ORTHOLOGOUS orthologous} statement.
  
  @param stmt {@link Statement} to evaluate
  @return {@code true} if it is valid, {@code false} otherwise