<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def tokenize(self, docs):
 """ Tokenizes a document, using a lemmatizer. Args: | doc (str) -- the text document to process. Returns: | list -- the list of tokens. """

        if self.n_jobs == 1:
            return [self._tokenize(doc) for doc in docs]
        else:
            return parallel(self._tokenize, docs, self.n_jobs)