def METHOD_NAME(self, main_tree):
    """Filters out Pre or NP that are in stop word list"""
    temp = [sub_tree for sub_tree in main_tree if toolbox.is_tree(sub_tree)]
    pres = [element for element in temp if element.label() == 'PRE']
    stop = set(stopwords.words('english'))
    for pre in pres:
        word = pre[0][0]
        if word in stop:
            main_tree.remove(pre)
    return main_tree