The initial route cannot be popped off the navigator, which implies that
this function returns true only if popping the navigator would not remove
the initial route.
Consults the current route's Route.willPop method, and acts accordingly,
potentially popping the route as a result; returns whether the pop request
should be considered handled.
Push the route with the given name onto the navigator that most tightly
encloses the given context, and then remove all the previous routes until
the predicate returns true.
Replace the current route of the navigator that most tightly encloses
the given context by pushing the given route and then disposing
the previous route once the new route has finished animating in.
Replace the current route of the navigator that most tightly encloses the
given context by pushing the route named routeName and then disposing the
previous route once the new route has finished animating in.