Viewers turned streamers

# Table: Sessions
# 
# +---------------+----------+
# | Column Name   | Type     |
# +---------------+----------+
# | user_id       | int      |
# | session_start | datetime |
# | session_end   | datetime |
# | session_id    | int      |
# | session_type  | enum     |
# +---------------+----------+
# session_id is column of unique values for this table.
# session_type is an ENUM (category) type of (Viewer, Streamer).
# This table contains user id, session start, session end, session id and session type.
# 
# Write a solution to find the number of streaming sessions for users whose first session was as a viewer.
# 
# Return the result table ordered by count of streaming sessions,  user_id in descending order.
# 
# The result format is in the following example.
#
# Example 1:
# Input:
# Sessions table:
# +---------+---------------------+---------------------+------------+--------------+
# | user_id | session_start       | session_end         | session_id | session_type |
# +---------+---------------------+---------------------+------------+--------------+
# | 101     | 2023-11-06 13:53:42 | 2023-11-06 14:05:42 | 375        | Viewer       |
# | 101     | 2023-11-22 16:45:21 | 2023-11-22 20:39:21 | 594        | Streamer     |
# | 102     | 2023-11-16 13:23:09 | 2023-11-16 16:10:09 | 777        | Streamer     |
# | 102     | 2023-11-17 13:23:09 | 2023-11-17 16:10:09 | 778        | Streamer     |
# | 101     | 2023-11-20 07:16:06 | 2023-11-20 08:33:06 | 315        | Streamer     |
# | 104     | 2023-11-27 03:10:49 | 2023-11-27 03:30:49 | 797        | Viewer       |
# | 103     | 2023-11-27 03:10:49 | 2023-11-27 03:30:49 | 798        | Streamer     |
# +---------+---------------------+---------------------+------------+--------------+
# Output:
# +---------+----------------+
# | user_id | sessions_count |
# +---------+----------------+
# | 101     | 2              |
# +---------+----------------+
# Explanation
# - user_id 101, initiated their initial session as a viewer on 2023-11-06 at 13:53:42, followed by two subsequent sessions as a Streamer, the count will be 2.
# - user_id 102, although there are two sessions, the initial session was as a Streamer, so this user will be excluded.
# - user_id 103 participated in only one session, which was as a Streamer, hence, it won't be considered.
# - User_id 104 commenced their first session as a viewer but didn't have any subsequent sessions, therefore, they won't be included in the final count.
# Output table is ordered by sessions count and user_id in descending order.

import pandas as pd

def count_turned_streamers(sessions: pd.DataFrame) -> pd.DataFrame:
  sessions = sessions.sort_values(['user_id', 'session_start'])
  first_session = sessions.groupby('user_id').first().reset_index()
  viewer_first = first_session[first_session['session_type'] == 'Viewer']['user_id']
  streamer_sessions = sessions[(sessions['user_id'].isin(viewer_first)) & (sessions['session_type'] == 'Streamer')]
  counts = streamer_sessions.groupby('user_id').size().reset_index(name='sessions_count')
  counts = counts[counts['sessions_count'] > 0]
  return counts.sort_values(['sessions_count', 'user_id'], ascending=[False, False])