src/main/java/com/googlecode/objectify/impl/Keys.java
public <T> Key<T> createKeyAny(final Key<?> parent, final Class<T> kind, final Object id) {
		if (id instanceof String)
			return createKey(parent, kind, (String)id);
		else if (id instanceof Long)
			return createKey(parent, kind, (Long)id);
		else
			throw new IllegalArgumentException("id '" + id + "' must be String or Long");
	}
public <T> Key<T> createKeyAny(final Key<?> parent, final Class<T> kind, final Object id) {
		if (id instanceof String)
			return createKey(parent, kind, (String)id);
		else if (id instanceof Long)
			return createKey(parent, kind, (Long)id);
		else
			throw new IllegalArgumentException("id '" + id + "' must be String or Long");
	}
Construct a Key<?> from a Long or String id
@param id must be either Long or String