Write a function count_pos that takes a two-dimensional list of integers as a parameter and returns the number of elements in the list that are positive. If there are no positive numbers in the list, then the function should return 0.

>>> count_pos([[3, 6, -1], [4], [3, -5, 0]])

4

>>> count_pos([[-1, 0]])

0

use python 3.7.0)