code: def src_dot_dst(src_field, dst_field, out_field):
      """
      This function serves as a surrogate for `src_dot_dst` built-in apply_edge function.
      """
  
      def func(edges):
          return {
              out_field: (
                  edges.src[src_field] * edges.dst[dst_field]
              ).sum(-1, keepdim=True)
          }
  
      return func
  
label_desc: Use image node_id 1 for calling a global function with example usage: src_dot_dst(src_field, dst_field, out_field) and returns: func, dict