input: Write a function to calculate the average of the elements in a 2-dimensional array. If the matrix is empty, return 0.
  def averageMatrix(matrix):
      if not matrix:
          return 0
      total = 0
      count = 0
      for row in matrix:
          for element in row:
              total += element
              count += 1
      return total / count
  
  a = [[3,2,6],
       [8,5,9],
       [4,7,1]]
  
  assert averageMatrix(a) == 5.0
  assert averageMatrix([[1,2,3],[4,5,6]]) == 3.5
  assert averageMatrix([[7,8],[9,10]]) == 8.5
  assert averageMatrix([]) == 0
  assert averageMatrix([[1]]) == 1.0
  assert averageMatrix([[1,2],[3,4],[5,6]]) == 3.5
output: def averageMatrix(matrix):
      if not matrix:
          return 0
      total = 0
      count = 0
      for row in matrix:
          for element in row:
              total += element
              count += 1
      return total / count