Write a function in python called three_most_common_hashtags_combined(data,usernames) -> list

Answers the question What are the most common hashtags used by users collectively? Return an ordered

list of three (count, hashtag) tuples where count is the count of all occurrences of hashtag across all

users in usernames. The three tuples in the list represent the three highest counts (and the hashtag) with

highest first. Hint: call get_histogram_tag_count_for_users and convert that dictionary to a sorted

list of tuples, largest first, and return the first three (slicing!).