code: function createEdge(
    store: RecordSourceProxy,
    record: RecordProxy,
    node: RecordProxy,
    edgeType: string,
  ): RecordProxy {
    const {NODE} = RelayConnectionInterface.get();
  
    // An index-based client ID could easily conflict (unless it was
    // auto-incrementing, but there is nowhere to the store the id)
    // Instead, construct a client ID based on the connection ID and node ID,
    // which will only conflict if the same node is added to the same connection
    // twice. This is acceptable since the `insertEdge*` functions ignore
    // duplicates.
    const edgeID = generateClientID(record.getDataID(), node.getDataID());
    let edge = store.get(edgeID);
    if (!edge) {
      edge = store.create(edgeID, edgeType);
    }
    edge.setLinkedRecord(node, NODE);
    return edge;
  }
docs: @public
  
  Creates an edge for a connection record, given a node and edge type.