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_dimension(cls, dataset, dimension, dim_pos, values, vdim):
        data = dataset.data.copy()
        if dimension.name not in data:
            data[dimension.name] = values
        return data