input: Write a function to calculate the average of the elements in a 2-dimensional array. The function should return the average as a floating-point number.
  def averageMatrix(matrix):
      sum = 0
      for row in matrix:
          for e in row:
              sum += e
      return sum / (len(matrix) * len(matrix[0]))
  
  assert averageMatrix([[3,2,6],[8,5,9],[4,7,1]])==5.0
  assert averageMatrix([[1,2],[3,4]])==2.5
  assert averageMatrix([[10],[20]])==15.0
  assert averageMatrix([])==0
  assert averageMatrix([[1,1,1],[1,1,1]])==1.0
output: def averageMatrix(matrix):
      if not matrix:
          return 0
      sum = 0
      count = 0
      for row in matrix:
          for e in row:
              sum += e
              count += 1
      return sum / count