def METHOD_NAME(self, rij):
    """
    Calculate cutoff function for all rij
    Args:
        rij (:obj:`torch.Tensor`): Pairwise distances of all pairs in this batch, size 
                                   (num_neighs, 1) where `num_neighs` is number of neighbors 
                                   for all atoms in this batch.
    """
    c = self.cutoff
    function = 0.5 + 0.5*torch.cos(self.pi*(rij-0)/(c-0))
    return function[:,0]