code: public Object getOverride(String operation) {
          Object result = null;
  
          if (this.overrideOnce.containsKey(operation) == true) {
              result = this.overrideOnce.get(operation);
              this.overrideOnce.remove(operation);
          } else if (this.override.containsKey(operation) == true) {
              result = this.override.get(operation);
          }
  
          return result;
      }
docs: Return override value
  
  @param operation name of the operation
  @return override value