input: Write a python function to search for documents containing a query string.
  assert search("apple") == ["apple pie", "apple tart"]
  assert search("banana") == ["banana bread", "banana smoothie"]
  assert search("cherry") == ["cherry pie", "cherry tart", "cherry smoothie"]
output: def search(query):
      documents = [
          "apple pie",
          "apple tart",
          "banana bread",
          "banana smoothie",
          "cherry pie",
          "cherry tart",
          "cherry smoothie",
      ]
      return [doc for doc in documents if query in doc]