code: public void setAccessToken(String accessToken, String tokenType) throws HelloSignException {
          if (accessToken == null) {
              throw new HelloSignException("Access Token cannot be null");
          }
          if (tokenType == null) {
              throw new HelloSignException("Token Type cannot be null");
          }
          this.accessToken = new String(accessToken);
          this.accessTokenType = new String(tokenType);
      }
docs: Sets the access token for the HelloSign client authentication.
  
  @param accessToken String
  @param tokenType String
  @throws HelloSignException if either the accessToken or tokenType are
  null