code: @Override
      @SuppressWarnings("unchecked")
      public <V> Property<V> property(String key) {
          Objects.requireNonNull(key, "key cannot be null");
          // property value
          Neo4JEdgeProperty propertyValue = properties.get(key);
          if (propertyValue != null)
              return (Property<V>)propertyValue;
          // empty property
          return Property.empty();
      }
docs: {@inheritDoc}