Return fit_params with added "sample_weight" argument.
    Unlike `fit_params['sample_weight'] = sample_weight` it
    handles a case where ``clf`` is a pipeline.

def with_sample_weight(clf, sample_weight, fit_params):
    """
    Return fit_params with added "sample_weight" argument.
    Unlike `fit_params['sample_weight'] = sample_weight` it
    handles a case where ``clf`` is a pipeline.
    """
    param_name = _get_classifier_prefix(clf) + "sample_weight"
    params = {param_name: sample_weight}
    params.update(fit_params)
    return params