Write a program that prints a "null matrix" as a nested list, based on user input of the matrix dimensions in the form x , where the first integer is the number of rows and the second is the number of columns. For example, with input 2 x 3 the output would be [ [0, 0, 0], [0, 0, 0] ] To complete this lab, you should complete only the definition of the matrix() function, whose single positional parameter is a tuple whose first element is the number of rows and whose second is the number of columns. You should not need to edit anything in the _main__block. 1 def matrix(dim): 2 your code goes here 3 return mat 4 5 if _name__ ' __main__': 6 "' The statement below creates the tuple matdim with (row, column) 7 matdim = [int(i) for i in input().split("x")] 8 nullmat - matrix(matdim) 9 print(nullmat)