code: public boolean containsValue(CharSequence name, CharSequence value, boolean ignoreCase) {
          Iterator<? extends CharSequence> itr = valueCharSequenceIterator(name);
          while (itr.hasNext()) {
              if (containsCommaSeparatedTrimmed(itr.next(), value, ignoreCase)) {
                  return true;
              }
          }
          return false;
      }
docs: Returns {@code true} if a header with the {@code name} and {@code value} exists, {@code false} otherwise.
  This also handles multiple values that are separated with a {@code ,}.
  <p>
  If {@code ignoreCase} is {@code true} then a case insensitive compare is done on the value.
  @param name the name of the header to find
  @param value the value of the header to find
  @param ignoreCase {@code true} then a case insensitive compare is run to compare values.
  otherwise a case sensitive compare is run to compare values.