text: """
  Attributes
  ----------
  file_name : str
  file_position : int
  """
  
  variables = ['file_name', 'file_position']
  
  def netcdfplus_init(store):
      store.create_variable(
          'file_name',
          'str',
          description="the file name that this snapshot is stored in"
      )
      store.create_variable(
          'file_position',
          'int',
          description="position within the file to find this trajectory"
      )
  
  