input: 
  def averageMatrix(matrix) -> float:
   """ Calculate the average of the elements in a 2-dimensional array.
   >>> averageMatrix([[3, 2, 6], [8, 5, 9], [4, 7, 1]])
   4.77
   """
   sum = 0
   for row in matrix:
    for e in row:
     sum += e
  
   return sum / (len(matrix) * len(matrix[0]))
  
output:     sum = 0
      for row in matrix:
          for e in row:
              sum += e
  
      return round(sum / (len(matrix) * len(matrix[0])), 2)