def faces_sparse(self):
        """
        A sparse matrix representation of the faces.

        Returns
        ----------
        sparse : scipy.sparse.coo_matrix
          Has properties:
          dtype : bool
          shape : (len(self.vertices), len(self.faces))
        """
        sparse = geometry.index_sparse(
            column_count=len(self.vertices),
            indices=self.faces)
        return sparse
A sparse matrix representation of the faces.

        Returns
        ----------
        sparse : scipy.sparse.coo_matrix
          Has properties:
          dtype : bool
          shape : (len(self.vertices), len(self.faces))