def select_mask(cls, dataset, selection):
        """
        Given a Dataset object and a dictionary with dimension keys and
        selection keys (i.e tuple ranges, slices, sets, lists or literals)
        return a boolean mask over the rows in the Dataset object that
        have been selected.
        """
        mask = np.ones(len(dataset), dtype=np.bool)
        for dim, k in selection.items():
            if isinstance(k, tuple):
                k = slice(*k)
            arr = cls.values(dataset, dim)
            if isinstance(k, slice):
                with warnings.catch_warnings():
                    warnings.filterwarnings('ignore', r'invalid value encountered')
                    if k.start is not None:
                        mask &= k.start <= arr
                    if k.stop is not None:
                        mask &= arr < k.stop
            elif isinstance(k, (set, list)):
                iter_slcs = []
                for ik in k:
                    with warnings.catch_warnings():
                        warnings.filterwarnings('ignore', r'invalid value encountered')
                        iter_slcs.append(arr == ik)
                mask &= np.logical_or.reduce(iter_slcs)
            elif callable(k):
                mask &= k(arr)
            else:
                index_mask = arr == k
                if dataset.ndims == 1 and np.sum(index_mask) == 0:
                    data_index = np.argmin(np.abs(arr - k))
                    mask = np.zeros(len(dataset), dtype=np.bool)
                    mask[data_index] = True
                else:
                    mask &= index_mask
        return mask
Given a Dataset object and a dictionary with dimension keys and
        selection keys (i.e tuple ranges, slices, sets, lists or literals)
        return a boolean mask over the rows in the Dataset object that
        have been selected.