input: Write a python function to respond to questions using a predefined dictionary of responses.
  assert respond_to_question("what is python") == "Python is a high-level programming language."
  assert respond_to_question("who created python") == "Python was created by Guido van Rossum in 1991."
  assert respond_to_question("what is java") == "Java is a class-based, object-oriented programming language."
  assert respond_to_question("who created java") == "Java was created by James Gosling in 1995."
output: def respond_to_question(question):
      responses = {
          "what is python": "Python is a high-level programming language.",
          "who created python": "Python was created by Guido van Rossum in 1991.",
          "what is java": "Java is a class-based, object-oriented programming language.",
          "who created java": "Java was created by James Gosling in 1995."
      }
      return responses.get(question.lower(), "I don't know the answer to that question.")