input: def read_data_from_json(filename):
      """Handle errors while reading data from a JSON file.
      If the file does not exist, print "The file specified does not exist."
      If the file is not in a valid JSON format, print "The file specified is not in a valid JSON format."
      >>> read_data_from_json('nonexistentfile.json')
      The file specified does not exist.
      >>> read_data_from_json('invalidjsonfile.json')
      The file specified is not in a valid JSON format.
      """
output:     import json
      import os
  
      if not os.path.exists(filename):
          print("The file specified does not exist.")
          return None
      
      try:
          with open(filename, 'r') as file:
              data = json.load(file)
              return data
      except json.JSONDecodeError:
          print("The file specified is not in a valid JSON format.")
          return None