input: Write a function to modify the given Python code to handle errors while reading data from a JSON file. The function should include error handling for cases where the file does not exist and where the file content is not a valid JSON format. If the file is not found, it should print a message "The file specified does not exist." If the file content is not a valid JSON, it should print a message "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.json") == None
  assert read_data_from_json("invalid.json") == None
  assert read_data_from_json("valid.json") != None
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.")