def METHOD_NAME(self, n_modes=20, zeros=False, turbo=True):
    """Calculate normal modes.  This method uses :func:`scipy.linalg.eigh`
    function to diagonalize the Hessian matrix. When Scipy is not found,
    :func:`numpy.linalg.eigh` is used.
    :arg n_modes: number of non-zero eigenvalues/vectors to calculate.
        If **None** is given, all modes will be calculated.
    :type n_modes: int or None, default is 20
    :arg zeros: If **True**, modes with zero eigenvalues will be kept.
    :type zeros: bool, default is **True**
    :arg turbo: Use a memory intensive, but faster way to calculate modes.
    :type turbo: bool, default is **True**
    """
    if n_modes is None:
        n_modes = self._dof
    super(RTB, self).METHOD_NAME(n_modes, zeros, turbo)
    self._array = np.dot(self._project, self._array)