code: EdgeLabel addEdgeLabel(
              String edgeLabelName,
              VertexLabel inVertexLabel,
              Map<String, PropertyType> properties) {
          return addEdgeLabel(edgeLabelName, inVertexLabel, properties, new ListOrderedSet<>());
      }
docs: Called via {@link Schema#ensureEdgeLabelExist(String, VertexLabel, VertexLabel, Map)}
  This is called when the {@link EdgeLabel} does not exist and needs to be created.
  
  @param edgeLabelName The edge's label.
  @param inVertexLabel The edge's in vertex.
  @param properties    The edge's properties.
  @return The new EdgeLabel.