code: def activate_program(self, program):
          
          self.logger.debug("activate_program %s", program)
          if program in self.program_stack:
              return
  
          with self._program_lock:
              self.logger.debug("activate_program got through %s", program)
              self.program_stack.append(program)
              self._update_program_stack()
docs: Called by program which desires to manipulate this actuator, when it is activated.