### Question:
SequenceItem implements VertexDictionary { public <T extends Vertex<?, ?>> T add(T v) { return add(v.getLabel(), v); } SequenceItem(int index, int uniqueSequenceIdentifier);  SequenceItem(int index, int uniqueSequenceIdentifier, String sequenceName); void addAll(T... vertices); void addAll(Collection<T> vertices); void addAll(Map<VertexLabel, T> vertices); T add(T v); T add(VertexLabel label, T v); Map<VertexLabel, Vertex<?, ?>> getContents(); int getIndex(); @Override V get(VertexLabel label); @Override SequenceItem withExtraEntries(Map<VertexLabel, Vertex<?, ?>> extraEntries); Collection<Vertex<?, ?>> getProxyVertices(); DoubleProxyVertex addDoubleProxyFor(VertexLabel label); DoubleProxyVertex addDoubleProxyFor(VertexLabel label, long[] shape); IntegerProxyVertex addIntegerProxyFor(VertexLabel label); IntegerProxyVertex addIntegerProxyFor(VertexLabel label, long[] shape); BooleanProxyVertex addBooleanProxyFor(VertexLabel label); BooleanProxyVertex addBooleanProxyFor(VertexLabel label, long[] shape);  }### Answer:
@Test public void itThrowsIfYouAddAVertexWithNoLabel() { expectedException.expect(SequenceConstructionException.class); expectedException.expectMessage(endsWith(" must contain a label in order to be added to a sequence item")); item.add(ConstantVertex.of(1.)); }