def __init__(self, groups=None):
        super(GroupedRequirements, self).__init__(NamedRequirements)
        self.groups = groups or self.default_groups
        self.filename = None
        self.create_default_groups()
def add_item(self, item_value=None, index=None):
    if item_value is None:
      item_value = self._new_item_default_value