Write a function that converts a sentence into Pig Latin (https://en.m.wikipedia.org/wiki/Pig_Latin#Rules).

pig_latin.py

def _to_pig_latin(word: str):
    """Converts the word into Pig Latin."""
    VOWELS = 'aeiou'
    if word[0].lower() in VOWELS:
        return f'{word}yay'
    
    consonants = 0
    for letter in word.lower():
        if letter not in VOWELS:
            consonants += 1
            continue
        return f'{word[consonants:]}{word[:consonants]}ay'


def to_pig_latin(sentence: str):
    """Converts the sentence into Pig Latin."""
    pig_latin_sentence = [_to_pig_latin(word) for word in sentence.split()]
    return ' '.join(pig_latin_sentence)


if __name__ == '__main__':
    CASES = (
        ('pig', 'igpay'),
        ('latin', 'atinlay'),
        ('banana', 'ananabay'),
        ('smile', 'ilesmay'),
        ('string', 'ingstray'),
        ('stupid', 'upidstay'),
        ('eat', 'eatyay'),
        ('omelet', 'omeletyay'),
        ('are', 'areyay'),
        ('I love Cassidy newsletter', 'Iyay ovelay assidyCay ewsletternay'),
    )

    for sentence, expected in CASES:
        result = to_pig_latin(sentence)
        assert result == expected, f'{result} != {expected}'