new_contents: 
  class Network:
      """Defines the eDisGo Network
  
      Used as container for all data related to a single MV grid.
  
      Attributes
      ----------
      _id : :obj:`str`
          Name of network
      _equipment_data : :obj:`dict` of `pandas.core.frame.DataFrame`
          Electrical equipment such as lines and transformers
      _config : ???
      _metadata : :obj:`dict`
          Metadata of Network such as
      _data_source : :obj:`str`
          Data Source of grid data (e.g. "dingo")
      _scenario : `edisgo.grid.network.Scenario`
          Scenario which is used for calculations
      _mv_grid : `edisgo.grid.grids.MVGrid`
          Medium voltage (MV) grid
      """
  
      def __init__(self, **kwargs):
          self._id = kwargs.get('id', None)
          self._equipment_data = kwargs.get('equipment_data', None)
          self._config = kwargs.get('config', None)
          self._metadata = kwargs.get('metadata', None)
          self._data_source = kwargs.get('data_source', None)
          self._scenarios = kwargs.get('scenarios', None)
          self._mv_grid = kwargs.get('mv_grid', None)
  
  
  class Scenario:
      """Defines an eDisGo scenario
  
      It contains
  
      Attributes
      ----------
      _scenario : :obj:`str`
          Scenario name (e.g. "feedin case weather 2011")
      _timeseries : :obj:`list` of `edisgo.grid.network.TimeSeries`
          Time series associated to a scenario
      _etrago_spec : `edisgo.grid.network.eTraGoSpec`
          Specifications which are to be fulfilled at transition point (HV-MV substation)
      _pfac_mv_gen : :obj:`float`
          Power factor for medium voltage generators
      _pfac_mv_load : :obj:`float`
          Power factor for medium voltage loads
      _pfac_lv_gen : :obj:`float`
          Power factor for low voltage generators
      _pfac_lv_load : :obj:`float`
          Power factor for low voltage loads
      """
  
      def __init__(self, **kwargs):
          self._scenario = kwargs.get('scenario', None)
          self._timeseries = kwargs.get('timeseries', None)
          self._etrago_spec = kwargs.get('etrago_spec', None)
          self._pfac_mv_gen = kwargs.get('pfac_mv_gen', None)
          self._pfac_mv_load = kwargs.get('pfac_mv_load', None)
          self._pfac_lv_gen = kwargs.get('pfac_lv_gen', None)
          self._pfac_lv_load = kwargs.get('pfac_lv_load', None)
  
  
  class TimeSeries:
      """Defines an eDisGo time series
  
      Attributes
      ----------
      _scenario : :obj:`str`
          Scenario name (e.g. "feedin case weather 2011")
      _pfac_mv_gen : :obj:`float`
          Power factor for medium voltage generators
      _pfac_mv_load : :obj:`float`
          Power factor for medium voltage loads
      _pfac_lv_gen : :obj:`float`
          Power factor for low voltage generators
      _pfac_lv_load : :obj:`float`
          Power factor for low voltage loads
      """
  
      def __init__(self, **kwargs):
          self._id = kwargs.get('id', None)
  
  
  class eTraGoSpec:
      """
  
      Specifications which are to be fulfilled at transition point (HV-MV substation)
  
      """
  
      def __init__(self, **kwargs):
          self._id = kwargs.get('id', None)
subject: add first, unfinished version of some basic classes