# NOT RUN {
 n <- addTaskCallback(function(expr, value, ok, visible) {
                        cat("In handler\n")
                        return(TRUE)
                      }, name = "simpleHandler")
 getTaskCallbackNames()
   # now remove it by name
 removeTaskCallback("simpleHandler")
 h <- taskCallbackManager()
 h$add(function(expr, value, ok, visible) {
                        cat("In handler\n")
                        return(TRUE)
                      }, name = "simpleHandler")
 getTaskCallbackNames()
 removeTaskCallback("R-taskCallbackManager")
# }
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