input: Write a function to classify text input based on given labels.
  assert classify_input_text("I am going to the store to buy groceries.", ["grocery shopping", "shopping", "going to the store"]) == "grocery shopping"
  assert classify_input_text("I love shopping on weekends.", ["grocery shopping", "shopping", "going to the store"]) == "shopping"
  assert classify_input_text("We are planning on going to the store later.", ["grocery shopping", "shopping", "going to the store"]) == "going to the store"
  assert classify_input_text("No matching labels here.", ["grocery shopping", "shopping", "going to the store"]) == None
output: def classify_input_text(text, labels):
      for label in labels:
          if label in text:
              return label
      return None