input: 
  def averageMatrix(matrix):
      """ 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 round(sum / (len(matrix) * len(matrix[0])), 2)
  
  a = [[3, 2, 6],
       [8, 5, 9],
       [4, 7, 1]]
  
  print(averageMatrix(a))
  
output:     sum = 0
      for row in matrix:
          for e in row:
              sum += e
  
      return round(sum / (len(matrix) * len(matrix[0])), 2)