A function to run before the given edge is detached from the given source vertex. If this method returns false, the detach will be aborted. The difference between this and
beforeDetach is that this method is fired as soon as a user tries to detach an edge from an endpoint in the UI, whereas
beforeDetach allows a user to detach the edge in the UI.
export declare type BeforeStartDetachInterceptor = (source: Vertex, edge: Edge) => any;