old_contents: class Load:
      """Load object """
  
      def __init__(self, **kwargs):
          self._id = kwargs.get('id', None)
          self._timeseries = kwargs.get('timeseries', None)
          self._geom = kwargs.get('geom', None)
          self._consumption = kwargs.get('consumption', None)
  
  
  
new_contents: class Load:
      """Load object """
  
      def __init__(self, **kwargs):
          self._id = kwargs.get('id', None)
          self._timeseries = kwargs.get('timeseries', None)
          self._geom = kwargs.get('geom', None)
          self._consumption = kwargs.get('consumption', None)
  
  
  class Generator:
      """Generator object"""
  
      def __init__(self, **kwargs):
          self._id = kwargs.get('id', None)
          self._geom = kwargs.get('geom', None)
          self._nominal_capacity = kwargs.get('nominal_capacity', None)
          self._type = kwargs.get('type', None)
          self._subtype = kwargs.get('subtype', None)
          self._timeseries = kwargs.get('timeseries', None)
  
subject: Add Generator class definition