input: Write a function to handle errors in reading JSON data from a file. The function should attempt to open the file, read the data, and return it. If the file does not exist, it should print a message stating that the file specified does not exist. If the file is not in a valid JSON format, it should print a message stating that the file specified is not in a valid JSON format.
  assert read_data_from_json("existing.json")=={"key": "value"}
  assert read_data_from_json("nonexistent.json")=="The file specified does not exist."
  assert read_data_from_json("invalid.json")=="The file specified is not in a valid JSON format."
  assert read_data_from_json("valid.json")=={"another_key": "another_value"}
output: def read_data_from_json(filename):
      try:
          with open(filename, 'r') as file:
              data = json.load(file)
              return data
      except FileNotFoundError:
          return "The file specified does not exist."
      except json.JSONDecodeError:
          return "The file specified is not in a valid JSON format."