input: Write a function to calculate the average of elements in a 2-dimensional array. The function should iterate through all elements of the matrix, sum them up, and then divide by the total number of elements to get the average. Return the average value.
  
  def averageMatrix(matrix):
   sum = 0
   for row in matrix:
    for e in row:
     sum += e
  
   return sum / (len(matrix) * len(matrix[0]))
  
  a = [[3,2,6],
       [8,5,9],
       [4,7,1]]
  
  assert averageMatrix(a) == 5.0
  assert averageMatrix([[1, 2], [3, 4]]) == 2.5
  assert averageMatrix([[0, 0], [0, 0]]) == 0.0
  assert averageMatrix([[10, 20], [30, 40]]) == 25.0
  assert averageMatrix([[1]]) == 1.0
output: def averageMatrix(matrix):
   sum = 0
   for row in matrix:
    for e in row:
     sum += e
  
   return sum / (len(matrix) * len(matrix[0]))