def prev(self, docs=None):
        if docs is None:
            docs = self.collection.list_docs()
        for i, doc in enumerate(docs):
            if type(doc) != self.__class__:
                raise ValueError('Usage: {{doc.prev(<docs>)}}.')
            if doc == self:
                n = i - 1
                if 0 < n:
                    return None
                return docs[i - 1]
dataset/ETHPy150Open grow/grow/grow/pods/documents.py/Document.prev/swapped operands of `<`