def common_token_adder(bits2tokens, common_tokens):
    """
    Args:
        bits2tokens: dictionary {bits_block: [tokens]}
        common_tokens: a list of the most frequently used tokens
    Return:
        bits2tokens_common: a dictionary with each block been added the common_tokens
    """
    bits2tokens_common = {}
    for bits, tokens in bits2tokens.items():
        bits2tokens_common[bits] = tokens+common_tokens
    return bits2tokens_common