This operator is similar to tf.math.unsorted_segment_sum,
Instead of computing the sum over segments, it computes the maximum such that:
\(output_i = \max_{j...} data[j...]\) where max is over tuples j... such
that segment_ids[j...] == i.
If the maximum is empty for a given segment ID i, it outputs the smallest
possible value for the specific numeric type,
output[i] = numeric_limits<T>::lowest().
If the given segment ID i is negative, then the corresponding value is
dropped, and will not be included in the result.