docs: function stripProxyResHeaders(res) {
    return Object.entries(res.headers).reduce((memo, header) => {
      const [key, val] = header
      const invalid = [undefined, 'connection', 'content-encoding']
      if (invalid.indexOf(key) === -1) {
        memo[key] = val // eslint-disable-line
      }
      return memo
    }, {})
  }