input: from typing import Dict
  
  def read_data_from_json(filename: str) -> Dict:
      """
      Reads a JSON file and returns its contents as a dictionary. If the file does not exist or the content is not valid JSON, appropriate error messages are printed.
      >>> read_data_from_json('existing_file.json')
      {'data': 'some_data'}
      >>> read_data_from_json('non_existing_file.json')
      The file specified does not exist.
      >>> read_data_from_json('invalid_json_file.json')
      The file specified is not in a valid JSON format.
      """
      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.")
output:     return {}