code: private static void validateVarValue(String varValue) throws ApiException {
  		if (varValue == null) {
  			throw new ApiException(ApiException.Type.DOES_NOT_EXIST, PARAM_VAR_KEY);
  		}
  	}
docs: Validates that the value is non-{@code null}, that is, the variable exists.
  
  @param varValue the value of the variable to validate.
  @throws ApiException if the value is {@code null}.