input: 
  def averageMatrix(matrix):
      """ Calculate the average of the elements in a given 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
      count = 0
      for row in matrix:
          for e in row:
              sum += e
              count += 1
      return round(sum / count, 2)