AggregationLayer

AggregationLayer[f] represents a layer that aggregates an array of arbitrary rank into a vector, using the function f.

AggregationLayer[f, n] aggregates an array at level n.

AggregationLayer[f, n1;;n2] aggregates an array at levels n1 through n2.

AggregationLayer[f, {n1, n2, …}] aggregates an array at levels n1, n2, ….

Please visit the official Wolfram Language Reference for more details.