@Override
  public String toString() {
    StringBuilder builder =
        new StringBuilder(protocolVersion.toString()).append(" ").append(status);
    if (reason != null) builder.append(' ').append(reason);
    builder.append('\n');
    for (String field : headers.keySet()) {
      for (String value : valuesOrEmpty(headers, field)) {
        builder.append(field).append(": ").append(value).append('\n');
      }
    }
    if (body != null) builder.append('\n').append(body);
    return builder.toString();
  }
the HTTP protocol version

@return HTTP protocol version or empty if a client does not provide it
core/src/main/java/feign/TypedResponse.java