val headers =
      Headers.Builder()
        .add("foo: bar")
        .add(" foo: baz") // Name leading whitespace is trimmed.
        .add("foo : bak") // Name trailing whitespace is trimmed.
        .add("\tkey\t:\tvalue\t") // '\t' also counts as whitespace
        .add("ping:  pong  ") // Value whitespace is trimmed.
        .add("kit:kat") // Space after colon is not required.
        .build()

    }

    fun name(name: String) =
      apply {
        require(name.trim() == name) { "name is not trimmed" }
        this.name = name
      }

    fun value(value: String) =
      apply {
        require(value.trim() == value) { "value is not trimmed" }
        this.value = value
      }

    fun expiresAt(expiresAt: Long) =
      apply {
        var expiresAt = expiresAt