code: public UserGroupInformation get() throws IOException {
  
      final UserGroupInformation effectiveUGI =
          this.proxyUGI == null ? UserGroupInformation.getCurrentUser() : this.proxyUGI;
  
      if (LOG.isLoggable(Level.FINEST)) {
        LOG.log(Level.FINEST, "UGI: get: {0}", ugiToString("EFFECTIVE", effectiveUGI));
      }
  
      return effectiveUGI;
    }
docs: Get the YARN proxy user information. If not set, return the (global) current user.
  @return Proxy user group information, if set; otherwise, return current YARN user.
  @throws IOException if proxy user is not set AND unable to obtain current YARN user information.