code: public Optional<String> getHeader(String name) {
          PSequence<String> values = lowercaseHeaders.get(name.toLowerCase(Locale.ENGLISH));
          if (values == null || values.isEmpty()) {
              return Optional.empty();
          } else {
              return Optional.of(values.get(0));
          }
      }
docs: Get the header with the given name.
  
  The lookup is case insensitive.
  
  @param name The name of the header.
  @return The header value.