input: Write a function to modify the given Python code to handle errors. The function should return the data if the file can be successfully read and parsed as JSON, or print an error message if the file does not exist or 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('valid_file.json')=={"key": "value"}
  assert read_data_from_json('nonexistent_file.json')=="The file specified does not exist."
  assert read_data_from_json('invalid_file.json')=="The file specified is not in a valid JSON format."
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.")