Generate a random sentence
        :example 'Lorem ipsum dolor sit amet.'

        :param nb_words: around how many words the sentence should contain
        :param variable_nb_words: set to false if you want exactly ``nb``
            words returned, otherwise the result may include a number of words
            of ``nb`` +/-40% (with a minimum of 1)
        :param ext_word_list: a list of words you would like to have instead of
            'Lorem ipsum'.

        :rtype: str

def sentence(self, nb_words=6, variable_nb_words=True, ext_word_list=None):
        """
        Generate a random sentence
        :example 'Lorem ipsum dolor sit amet.'

        :param nb_words: around how many words the sentence should contain
        :param variable_nb_words: set to false if you want exactly ``nb``
            words returned, otherwise the result may include a number of words
            of ``nb`` +/-40% (with a minimum of 1)
        :param ext_word_list: a list of words you would like to have instead of
            'Lorem ipsum'.

        :rtype: str
        """
        if nb_words <= 0:
            return ''

        if variable_nb_words:
            nb_words = self.randomize_nb_elements(nb_words, min=1)

        words = self.words(nb=nb_words, ext_word_list=ext_word_list)
        words[0] = words[0].title()

        return self.word_connector.join(words) + self.sentence_punctuation