def METHOD_NAME(self, tokens):
    """Returns the list of lemma for list of tokens
    Args:
        tokens: list of strings to extract its lemma
    Returns:
        The list of lemma
        For example:
            lemma=Lemmatizer()
            output= lemma.lemmatize_tokens(['plays','boys'])
            print output
            >> ['play','boy']
    """
    lemma_list = []
    for token in tokens:
        lemma_list.append(self.lemmatize_word(token.lower().strip()))
    return lemma_list