input: Write a function to calculate the average of the elements in a 2-dimensional array. Return the average rounded to two decimal places.
  
  def averageMatrix(matrix):
      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]]
  
  assert averageMatrix(a) == 4.77
  assert averageMatrix([[1,2],[3,4]]) == 2.5
  assert averageMatrix([[0,0],[0,0]]) == 0.0
  assert averageMatrix([[1],[2],[3]]) == 2.0
  assert averageMatrix([]) == 0.0
output: def averageMatrix(matrix):
      if not matrix:
          return 0.0
      sum = 0
      count = 0
      for row in matrix:
          for e in row:
              sum += e
              count += 1
      return round(sum / count, 2)