code: public void alternateCalls(String connId, String heldConnId) throws WorkspaceApiException {
          this.alternateCalls(connId, heldConnId, null, null);
      }
docs: Alternate two calls so that you retrieve a call on hold and place the established call on hold instead.
  This is a shortcut for doing `holdCall()` and `retrieveCall()` separately.
  @param connId The connection ID of the established call that should be placed on hold.
  @param heldConnId The connection ID of the held call that should be retrieved.