If the result says that
unused was proven, there won't be a
new request set
delivered. Otherwise, the new request set delivered by
getNewRequestSet() is the request set updated by setting
a variable value in the remaining
UnusedEvaluationRequests as well as having removed those requests that were
evaluated due to the variable inference and that returned
false. Those requests whose evaluation was triggered
by the variable inference but which failed due to another unknown variable are entered again, this time with the now
unknown variable as key.