text: Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
  ### Context:
  CREATE TABLE visitor (age INTEGER, Level_of_membership VARCHAR)
  ### Question:
  What is the average age of the visitors whose membership level is not higher than 4?
  ### Answer:
  SELECT AVG(age) FROM visitor WHERE Level_of_membership <= 4