def extract_lock_token(if_header)
      token = if_header.scan(Calligraphy::LOCK_TOKEN_REGEX)
      token.flatten.first if token.is_a? Array
    end
def extract_lock_token(if_header)
      token = if_header.scan(Calligraphy::LOCK_TOKEN_REGEX)
      token.flatten.first if token.is_a? Array
    end
Extracts a lock token from an If headers.