Find there is an emoji in a string in python3

I want to check that a string contains only one emoji, using Python 3. For example, there is a is_emoji function that checks that the string has only one emoji.

def is_emoji(s):
    pass

is_emoji("😘") #True
is_emoji("😘◼️") #False

I try to use regular expressions but emojis didn't have fixed length. For example:

print(len("◼️".encode("utf-8"))) # 6 
print(len("😘".encode("utf-8"))) # 4

This works in Python 3:

def is_emoji(s):
    emojis = "😘◼️" # add more emojis here
    count = 0
    for emoji in emojis:
        count += s.count(emoji)
        if count > 1:
            return False
    return bool(count)

Test:

>>> is_emoji("😘")
True
>>> is_emoji('◼')
True
>>> is_emoji("😘◼️")
False

Combine with Dunes' answer to avoid typing all emojis:

from emoji import UNICODE_EMOJI

def is_emoji(s):
    count = 0
    for emoji in UNICODE_EMOJI:
        count += s.count(emoji)
        if count > 1:
            return False
    return bool(count)

This is not terrible fast because UNICODE_EMOJI contains nearly 1330 items, but it works.