code: def _brownian_eigs(n_grid, lag_time, grad_potential, xmin, xmax, reflect_bc):
      
      transmat = _brownian_transmat(n_grid, lag_time, grad_potential, xmin, xmax, reflect_bc)
      u, lv, rv = _solve_msm_eigensystem(transmat, k=len(transmat) - 1)
      return u, rv
docs: Analytic eigenvalues/eigenvectors for 1D Brownian dynamics