Function ftlm_observable_iteration 

pub fn ftlm_observable_iteration<O>(
    hamiltonian: &O,
    initial: &[Complex64],
    observables: &[(String, &dyn LinearOperator)],
    inverse_temperatures: &[f64],
    options: LanczosOptions,
) -> Result<ThermalObservableIteration>
where
    O: LinearOperator + ?Sized,

QuSpin-compatible one-sided FTLM observable estimates.