code: public List<String> getHeaderStringValues(String name) {
      Object value = get(name.toLowerCase(Locale.US));
      if (value == null) {
        return Collections.emptyList();
      }
      Class<? extends Object> valueClass = value.getClass();
      if (value instanceof Iterable<?> || valueClass.isArray()) {
        List<String> values = new ArrayList<String>();
        for (Object repeatedValue : Types.iterableOf(value)) {
          values.add(toStringValue(repeatedValue));
        }
        return Collections.unmodifiableList(values);
      }
      return Collections.singletonList(toStringValue(value));
    }
docs: Returns an unmodifiable list of the header string values for the given header name.
  
  @param name header name (may be any case)
  @return header string values or empty if not found
  @since 1.13