"""

(file1 file2) (tfidf1*tfidf2) --> (file1 file2) (cosine_similarity(f1, f2))

sums up the products of the tfidf values of words common between every

pair of documents to produce the cosine similarity of the two documents

"""

for in_key, key_stream in input:

sum_for_docs = 0

for in_value in key_stream:

sum_for_docs += in_value['product']

out_key = {'file1': in_key['file1'], 'file2': in_key['file2']}

out_value = {'cos_similarity': sum_for_docs}