def _get_subclasses(base_class):
    """Gets all of the leaf nodes in the hiearchy tree for a given base class.

    Args:
        base_class (abc.ABCMeta): Class to find all of the children for.

    Returns:
        subclasses (list): List of all children that are not base classes.
    """
    classes_to_check = base_class.__subclasses__()
    subclasses = []

    while classes_to_check:
        subclass = classes_to_check.pop()
        children = subclass.__subclasses__()

        if children:
            classes_to_check.extend(children)
        else:
            subclasses.append(subclass)

    return subclasses