input: Write a python function to make a search request to a search engine API and return the most relevant result.
  assert search_engine('python programming') == 'Most relevant result for python programming'
  assert search_engine('best python libraries') == 'Most relevant result for best python libraries'
  assert search_engine('how to learn python') == 'Most relevant result for how to learn python'
output: def search_engine(query):
      # This is a mock implementation since we cannot actually make API requests.
      return f'Most relevant result for {query}'