docs: private Statement relationPattern(Variable varName, Collection<RelationProperty.RolePlayer> relationPlayers) {
          Statement var = new Statement(varName);
          for (RelationProperty.RolePlayer rp : relationPlayers) {
              Statement rolePattern = rp.getRole().orElse(null);
              var = rolePattern != null? var.rel(rolePattern, rp.getPlayer()) : var.rel(rp.getPlayer());
          }
          return var;
      }