How to use the emoji.models.Emoji.replace function in emoji

def test_if_no_valid_emoji_return_unchanged(self):
        self.assertEqual(Emoji.replace(':ducklingdrinkingcoffee:'),
                         ':ducklingdrinkingcoffee:')

def test_replace_string_should_use_staticfiles_app(self):
        self.assertEqual(
            Emoji.replace(':+1:'),
            '<img class="emoji" alt="+1" src="/static/emoji/img/%2B1.png">'

def test_replace_string_with_emojis(self):
        test_string = '''It's raining :cat:s and :dog:s.'''
        replaced_string = Emoji.replace(test_string)
        self.assertTrue('cat.png' in replaced_string)
        self.assertTrue('dog.png' in replaced_string)

def test_replace_string_with_emojis_no_emoji_do_nothing(self):
        self.assertEqual(Emoji.replace('Hello.'), 'Hello.')