Using python 3.0 or greater. I need help writing this recursive function.

Write a recursive function that is able to tell if a pokemon can to evolve into a given target pokemon.

The function will have three parameters, a source, target and a dictionary containing the pokemon and their

evolutionary lineage. The source being the pokemon in question and the target being if the source pokemon can

evolve into the target pokemon. No de-evolution can take place.

Example of a dictionary.

book = {

"squirtle" : ["wartortle"], "wartortle" : ["blastoise"], "blastoise" : [], "eevee" : ["flareon", "jolteon", "vaporeon"]

}

"blastoise" : [], represents its final form and can't evolve anymore.

Here is what I got so far.

def evolution(source,target,book):  if book[source]==[]: return False   elif book[source]!= target: for x in book[source]: source=x return source elif book[source]== target: return True   else: return evolution(source,book[target],book) 

Thanks for the help.