import re


def normalize_char_sequences(sentence):
    """
    :param sentence:        str

    :return new_sentence:   str  --> sentence with normalized char sequences
                                     dropped to the second repetition
                                     e.g. Helllloooo -> Helloo
                                          Byeeee -> Byee
                                          Yeeees -> Yees
    """

    # take all the characters repeated from 2 to "n" times
    # replace them just with the first two chars
    new_sentence = re.sub(r'(.)\1{2,}', r'\1\1', sentence)

    return new_sentence