code: func (c *Context) GetStringMapStringSlice(key string) (smss map[string][]string) {
  	if val, ok := c.Get(key); ok && val != nil {
  		smss, _ = val.(map[string][]string)
  	}
  	return
  }
docs: // GetStringMapStringSlice returns the value associated with the key as a map to a slice of strings.