def groupby_type(estimators):
    """
    finds the number of estimators for each estimator class
    :param estimators: list of estimators (not necessarily trained)
    :return: a dictionary of estimator class as key and frequency as value
    """
    unique_classes = {}
    for estimator in estimators:
        clf_name = estimator.__class__.__name__
        if clf_name not in list(unique_classes.keys()):
            unique_classes[clf_name] = 0
        unique_classes[clf_name] += 1
    return unique_classes