code: @MapMethod
      public int length(Object o){
          if(o instanceof List){
              return ((List) o).size();
          }else if(o instanceof Map){
              return ((Map) o).size();
          }else if(o instanceof String){
              return ((String) o).length();
          }
          return 0;
      }
docs: Get string|list|map length
  
  @param o
  @return