def residual_histogram(df, col_true, col_pred=None):
    """
    Compute histogram of residuals of a predicted DataFrame.

    Note that this method will trigger the defined flow to execute.

    :param df: predicted data frame
    :type df: DataFrame
    :param col_true: column name of true value
    :type col_true: str
    :param col_true: column name of predicted value, 'prediction_score' by default.
    :type col_pred: str
    :return: histograms for every columns, containing histograms and bins.
    """
    if not col_pred:
        col_pred = get_field_name_by_role(df, FieldRole.PREDICTED_VALUE)
    return _run_evaluation_node(df, col_true, col_pred)['hist']
Compute histogram of residuals of a predicted DataFrame.

    Note that this method will trigger the defined flow to execute.

    :param df: predicted data frame
    :type df: DataFrame
    :param col_true: column name of true value
    :type col_true: str
    :param col_true: column name of predicted value, 'prediction_score' by default.
    :type col_pred: str
    :return: histograms for every columns, containing histograms and bins.