code: @Transformer
      public static int len(Object o) {
          if (o instanceof Collection) {
              return ((Collection)o).size();
          } else if (o instanceof Map) {
              return ((Map)o).size();
          } else if (o.getClass().isArray()) {
              return Array.getLength(o);
          } else {
              return str(o).length();
          }
      }
docs: get length of specified object
  
  <ul>
  <li>If o is a Collection or Map, then return size of it</li>
  <li>If o is an array, then return length of it</li>
  <li>Otherwise return length() of String representation of the object</li>
  </ul>
  @param o
  @return length