title: print just the key of I in dict
body: <p>so I am writing a program that when you give it a dictionary value it turns you it's key . the program consist of by giving the score of an allergy it tells you what allergy you got . I wrote the script but returns me None as result to my function . Can someone tell me what I should modify ?</p>
  <pre><code>def allergie(aller):
      listofallergies = {'eggs': 1 , 'peanuts':2 ,'shellfish': 4 , 'strawberries':8 , 'tomatoes': 16 , 'chocolat':32 , 'pollen': 64 , 'cats': 128 }
      if aller in listofallergies:
          print (listofallergies.keys(aller))
      else:
          return None 
  print (allergie(4)) 
  </code></pre>