如何基于字对的存在来选择子字符串?Python

I have a large number of sentences, from which I want to extract sub-sentences that start with certain word combinations. For example, I want to extract sentence segments that begin with "what does" or "what is', etc. (essentially eliminating the words from the sentence that appear before the word-pairs). Both the sentences and the word-pairs are stored in a I have a large number of sentences, from which