code: public SignatureRequest getSignatureRequest(String id) throws HelloSignException {
          String url = BASE_URI + SIGNATURE_REQUEST_URI + "/" + id;
          return new SignatureRequest(httpClient.withAuth(auth).get(url).asJson());
      }
docs: Retrieves a Signature Request with the given ID.
  
  @param id String signature ID
  @return SignatureRequest
  @throws HelloSignException thrown if there's a problem processing the
  HTTP request or the JSON response.