code: func (sc *Client) MarkTrustedPeer(ctx context.Context, enode string) error {
  	var ignored bool
  	return sc.c.CallContext(ctx, &ignored, "shh_markTrustedPeer", enode)
  }
docs: // MarkTrustedPeer marks specific peer trusted, which will allow it to send historic (expired) messages.
  // Note This function is not adding new nodes, the node needs to exists as a peer.