code: func (h Headers) Contains(k string) (string, bool) {
  	for i := 0; i < len(h); i += 2 {
  		if h[i] == k {
  			return h[i+1], true
  		}
  	}
  	return "", false
  }
docs: /*
  	Contains returns true if a set of Headers contains a key.
  */