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In the referenced bug Alexander suggests a couple of changes. This task is to partially adopt one of his changes: replacing Remove with Cancel everywhere. Your task is to two fold:

1. Apply these two patches
2. Check that ns-3 still builds. You should disable the Python bindings (--disable-python) if you normally have it enabled. It will fail because there are Remove() calls which have been added since these were last tested, so you'll have to fix these.
3. Check that all tests pass.
4. As discussed in the bug report, deliver a new patch that is the synthesis of the previous two patches, plus any additional changes that you made to get the ns-3 code to compile, but that reverts all the changes to src/core and src/mpi that were removing the Remove() method from the API of the different Scheduler and Timer implementations. To summarize, your final patch should not touch src/core or src/mpi, but everywhere else in the codebase, the models should use Cancel() instead of Remove().