input: Write a function to calculate the average of the elements in a 2-dimensional array. 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]])==4.77
  assert averageMatrix([[]])==0.0
  assert averageMatrix([[1,1,1], [1,1,1]])==1.0
  assert averageMatrix([[0,0,0], [0,0,0]])==0.0
  assert averageMatrix([[10,20], [30,40]])==25.0
output: def averageMatrix(matrix):
      if not matrix or not matrix[0]:
          return 0.0
      sum = 0
      count = 0
      for row in matrix:
          for e in row:
              sum += e
              count += 1
      return sum / count