def []=(key, value)
      key = self.class.normalize_key(key)
      if (header_class = self.class.attributes[key])
        value = header_class.parse(value)
      end
      super(key, value)
    end
def []=(key, value)
      key = self.class.normalize_key(key)
      if (header_class = self.class.attributes[key])
        value = header_class.parse(value)
      end
      super(key, value)
    end
Public: Associates key with value. If key is a valid HTTP Header name,
 like "Content-Type", it parses as HTTP Object.

 key - key or HTTP Header name.
 value - object. If key is HTTP Header name, value should be a String.