code: func ContentTypeIs(typ string, types ...string) RespCondition {
  	types = append(types, typ)
  	return RespConditionFunc(func(resp *http.Response, ctx *ProxyCtx) bool {
  		if resp == nil {
  			return false
  		}
  		contentType := resp.Header.Get("Content-Type")
  		for _, typ := range types {
  			if contentType == typ || strings.HasPrefix(contentType, typ+";") {
  				return true
  			}
  		}
  		return false
  	})
  }
docs: // ContentTypeIs returns a RespCondition testing whether the HTTP response has Content-Type header equal
  // to one of the given strings.