code: public void addWarning(Position pos, String message, Object... parameters) {
          getProblemCollector().add(ParseError.warning(pos, String.format(message, parameters)));
      }
docs: Adds a warning to the internal problem collector.
  <p>
  A warning indicates an anomaly which might lead to an error but still, the parser can continue to complete its
  work.
  
  @param pos        the position of the warning. Note that {@link Token} implements {@link Position}.
  Therefore the current token is often a good choice for this parameter.
  @param message    the message to describe the earning. Can contain formatting parameters like %s or %d as
  defined by {@link String#format(String, Object...)}
  @param parameters Contains the parameters used to format the given message