problems,
                        Severity.FATAL,
                        Version.V31,
                        prefix + "[" + key + "]",
                        key,
                        "is referencing itself.",
                        dependency);
            }
        }
    }

    private void validateEffectiveDependencies(
            ModelProblemCollector problems,
            Model m,

typedef struct TF_Graph TF_Graph;

// Return a new graph object.
TF_CAPI_EXPORT extern TF_Graph* TF_NewGraph(void);

// Destroy an options object. Graph will be deleted once no more
// TFSession's are referencing it.
TF_CAPI_EXPORT extern void TF_DeleteGraph(TF_Graph*);

// Operation being built. The underlying graph must outlive this.
typedef struct TF_OperationDescription TF_OperationDescription;

    WeakValueReference<K, V, E> getWeakValueReferenceForTesting(InternalEntry<K, V, ?> entry) {
      throw new AssertionError();
    }

    /**
     * Unsafely creates of a fresh {@link WeakValueReference}, referencing the given {@code value},
     * for the given {@code entry}
     */
    WeakValueReference<K, V, E> newWeakValueReferenceForTesting(
        InternalEntry<K, V, ?> entry, V value) {

    WeakValueReference<K, V, E> getWeakValueReferenceForTesting(InternalEntry<K, V, ?> entry) {
      throw new AssertionError();
    }

    /**
     * Unsafely creates of a fresh {@link WeakValueReference}, referencing the given {@code value},
     * for the given {@code entry}
     */
    WeakValueReference<K, V, E> newWeakValueReferenceForTesting(
        InternalEntry<K, V, ?> entry, V value) {