Make each string in the collection end with a unique character.
    Essential for correct builiding of a generalized annotated suffix tree.
    Returns the updated strings collection, encoded in Unicode.

    max strings_collection ~ 1.100.000

def make_unique_endings(strings_collection):
    """
    Make each string in the collection end with a unique character.
    Essential for correct builiding of a generalized annotated suffix tree.
    Returns the updated strings collection, encoded in Unicode.

    max strings_collection ~ 1.100.000
    
    """
    res = []
    for i in range(len(strings_collection)):
        # NOTE(msdubov): a trick to handle 'narrow' python installation issues.
        hex_code = hex(consts.String.UNICODE_SPECIAL_SYMBOLS_START+i)
        hex_code = r"\U" + "0" * (8 - len(hex_code) + 2) + hex_code[2:]
        res.append(strings_collection[i] + hex_code.decode("unicode-escape"))
    return res