public static MutableSerializationRegistry globalInstance() {
    return GLOBAL_INSTANCE;
  }
A Mutable version of the {@link SerializationRegistry}.

<p>This class probably shouldn't exist; it would be better if we had only the
SerializationRegistry. However, at the moment, we need this, since a call to e.g.

<pre> AesCmacKeyManager.register() </pre>

should register such an object into a global, mutable registry.
java_src/src/main/java/com/google/crypto/tink/internal/MutableSerializationRegistry.java