code: public Map<String, Object> createContext(final Map<String, Object> parent, Map<String, Object> current) {
          return new DelegateMap<String, Object>(parent, current) {
              private static final long serialVersionUID = 1L;
  
              @Override
              public Object get(Object key) {
                  Object value = super.get(key);
                  if (value == null && parent == null
                          && resolver != null) {
                      return resolver.get((String) key);
                  }
                  return value;
              }
          };
      }
docs: Create context map.
  
  @return context map