def METHOD_NAME(self):
    """
    @brief Boundary cell indicator.
    @return: A bool tensor with shape (NC, ) to indicate if a cell locats\
             next to the boundary.
    """
    NC = self.number_of_cells()
    edge2cell = self.edge2cell
    isBdCell = torch.zeros((NC,), dtype=torch.bool, device=self.device)
    isBdEdge = self.boundary_edge_flag()
    isBdCell[edge2cell[isBdEdge, 0]] = True
    return isBdCell