int sum(string prefix) {
   int sum = 0;
   for (auto it = m.begin(); it != m.end(); ++it) {
     if (prefixMatch(prefix, it->first)) {
       sum += it->second;
     }
   } 
   return sum;
 }
TEST(CSSTokenizerTest, MultipleCharacterTokens)
{
    TEST_TOKENS("~=", includeMatch());
    TEST_TOKENS("|=", dashMatch());
    TEST_TOKENS("^=", prefixMatch());
    TEST_TOKENS("$=", suffixMatch());
    TEST_TOKENS("*=", substringMatch());
    TEST_TOKENS("||", column());
    TEST_TOKENS("|||", column(), delim('|'));
    TEST_TOKENS("<!--", cdo());
    TEST_TOKENS("<!---", cdo(), delim('-'));
    TEST_TOKENS("-->", cdc());
}