def METHOD_NAME(self, k=6):  # pragma: no cover
    """Computes a tensor with the eigenvectors for the Hamiltonian.
    Args:
        k (int): Number of eigenvalues to calculate if the Hamiltonian
            was created using a sparse matrix. This argument is ignored
            if the Hamiltonian was created using a dense matrix.
            See :meth:`qibo.backends.abstract.AbstractBackend.eigh` for
            more details.
    """
    raise_error(NotImplementedError)