op. The order of ops will be preserved. Functions named `main` with no
    `tf.entry_function` attribute will not be pruned, as such graphs/functions may
    have been imported from a V1 TensorFlow graph, where feeds/fetches/targets are
    not provided at certain stages of IR transformation (e.g. pre-placement).

    Option `ops-to-preserve` allows to specify ops that should not be pruned,
    regardless of their reachability.