LDPC Error Floor Estimation Task Constraints:

1) Implement `TrappingSetSampler` class that inherits from `SamplerBase`.
2) Implement `simulate_variance_controlled()` method with the required signature.
3) The method must return a tuple or dict with: (errors_log, weights_log, err_ratio, total_samples, actual_std, converged).
4) Use importance sampling to bias toward noise vectors that cause trapping set failures.
5) The solution should estimate error floor BER accurately and efficiently.

