def load(cls, folder):
        """
        Loads PopulationSet from folder

        ``popset.h5`` and ``trsig.pkl`` must exist in folder.

        :param folder:
            Folder from which to load.
        """
        popset = PopulationSet.load_hdf(os.path.join(folder,'popset.h5'))
        sigfile = os.path.join(folder,'trsig.pkl')
        with open(sigfile, 'rb') as f:
            trsig = pickle.load(f)
        return cls(trsig, popset, folder=folder)