code: function GetHeadersPacket(locator, stop) {
    if (!(this instanceof GetHeadersPacket))
      return new GetHeadersPacket(locator, stop);
  
    GetBlocksPacket.call(this, locator, stop);
  }
docs: Represents a `getheaders` packet.
  @extends GetBlocksPacket
  @constructor
  @param {Hash[]} locator
  @param {Hash?} stop