@Override
  @Nullable
  public Integer getIdRequirementOrNull() {
    return serialization.getIdRequirementOrNull();
  }
Returns true if we are sure that the other key is the same.

<p>Due to the fact that proto key serialization isn't guaranteed to be deterministic, this
isn't guaranteed to be true in case two serializations are actually the same. This shouldn't be
a problem: the use of key equality is that one can implement keyset equality, which is useful
when one wants the guarantee that two keysets are the same (for example, when one changes the
source of the keyset from disk to a remotely stored keyset). Since the only thing which can
happen is that we falsely return "false", this can then be solved in debugging. (The
alternative would be to throw an UnsupportedOperationException while we add the real
implementations of keys)
java_src/src/main/java/com/google/crypto/tink/internal/LegacyProtoKey.java