* @brief Observable calls this method to check if observer interested or not in emissions * * @return true if observer disposed and

* @example retry.cpp **/

* @example delay.cpp **/

* @example take_last.cpp **/

* @example take_until.cpp **/

* @example combine_latest.cpp **/

* @example filter.cpp **/

* @example last.cpp **/

* @example multicast.cpp **/

* @example skip.cpp **/

* @example subscribe_on.cpp **/

* @example window.cpp **/