input: Write a function to modify the given Python code to handle errors. The function should open a specified filename and load data from it in JSON format. If the file does not exist, it should print "The file specified does not exist." If the file is not in a valid JSON format, it should print "The file specified is not in a valid JSON format."
  
  def read_data_from_json(filename):
      try:
          with open(filename, 'r') as f:
              data = json.load(f)
          return data
      except FileNotFoundError:
          print("The file specified does not exist.")
      except json.decoder.JSONDecodeError:
          print("The file specified is not in a valid JSON format.")
  
  assert read_data_from_json("nonexistent_file.json")=="The file specified does not exist."
  assert read_data_from_json("invalid_json_file.json")=="The file specified is not in a valid JSON format."
  assert read_data_from_json("valid_json_file.json")=={"key": "value"}
output: def read_data_from_json(filename):
      try:
          with open(filename, 'r') as f:
              data = json.load(f)
          return data
      except FileNotFoundError:
          print("The file specified does not exist.")
      except json.decoder.JSONDecodeError:
          print("The file specified is not in a valid JSON format.")