code: function(
          crypto_type, crypto_content, senderCurve25519Key, claimedEd25519Key,
      ) {
          // keep the plain-text data for 'view source'
          this._clearEvent = {
              type: this.event.type,
              content: this.event.content,
          };
          this.event.type = crypto_type;
          this.event.content = crypto_content;
          this._senderCurve25519Key = senderCurve25519Key;
          this._claimedEd25519Key = claimedEd25519Key;
      }
docs: Replace the content of this event with encrypted versions.
  (This is used when sending an event; it should not be used by applications).
  
  @internal
  
  @param {string} crypto_type type of the encrypted event - typically
  <tt>"m.room.encrypted"</tt>
  
  @param {object} crypto_content raw 'content' for the encrypted event.
  
  @param {string} senderCurve25519Key curve25519 key to record for the
  sender of this event.
  See {@link module:models/event.MatrixEvent#getSenderKey}.
  
  @param {string} claimedEd25519Key claimed ed25519 key to record for the
  sender if this event.
  See {@link module:models/event.MatrixEvent#getClaimedEd25519Key}