input: Write a function to find the maximum value within a nested dictionary.
  
  Input:
  sample_dict = {
      "key1": {
          "value1": 10,
          "value2": 20
      },
      "key2": {
          "value3": 40
      },
  }
  
  Output:
  def findMaxValue(dict):
      max_val = None
      for key, value in dict.items():
          if isinstance(value, dict):
              max_val = max(findMaxValue(value), max_val)
          else:
              max_val = max(value, max_val)
      return max_val
  
  print(findMaxValue(sample_dict))
output: def findMaxValue(dict):
      max_val = None
      for key, value in dict.items():
          if isinstance(value, dict):
              max_val = max(findMaxValue(value), max_val)
          else:
              max_val = max(value, max_val)
      return max_val