input: Write a python function to recognize speech from an audio file using the SpeechRecognition library.
  assert recognize_speech("sample_audio.wav") == "your expected text here"
  assert recognize_speech("another_audio.wav") == "another expected text"
  assert recognize_speech("different_audio.wav") == "some different expected text"
output: def recognize_speech(audio_file):
      import speech_recognition as sr
      
      recognizer = sr.Recognizer()
      
      with sr.AudioFile(audio_file) as source:
          audio = recognizer.record(source)
      
      try:
          text = recognizer.recognize_google(audio)
      except sr.UnknownValueError:
          text = "Could not understand audio"
      except sr.RequestError:
          text = "Could not request results"
      
      return text