code: public void writeClosePortal(String portal) {
      ensureBuffer();
      int pos = out.writerIndex();
      out.writeByte(CLOSE);
      out.writeInt(0);
      out.writeByte('P'); // 'S' to close a prepared statement or 'P' to close a portal
      Util.writeCStringUTF8(out, portal);
      out.setInt(pos + 1, out.writerIndex() - pos - 1);
    }
docs: <p>
  The message closes an existing prepared statement or portal and releases resources.
  Note that closing a prepared statement implicitly closes any open portals that were constructed from that statement.
  <p>
  The response is either {@link CloseComplete} or {@link ErrorResponse}
  
  @param portal