Grand slam titles

# Table: Players
# 
# +----------------+---------+
# | Column Name    | Type    |
# +----------------+---------+
# | player_id      | int     |
# | player_name    | varchar |
# +----------------+---------+
# player_id is the primary key (column with unique values) for this table.
# Each row in this table contains the name and the ID of a tennis player.
# 
#  
# 
# Table: Championships
# 
# +---------------+---------+
# | Column Name   | Type    |
# +---------------+---------+
# | year          | int     |
# | Wimbledon     | int     |
# | Fr_open       | int     |
# | US_open       | int     |
# | Au_open       | int     |
# +---------------+---------+
# year is the primary key (column with unique values) for this table.
# Each row of this table contains the IDs of the players who won one each tennis tournament of the grand slam.
# 
#  
# 
# Write a solution to report the number of grand slam tournaments won by each player. Do not include the players who did not win any tournament.
# 
# Return the result table in any order.
# 
# The result format is in the following example.
#
# Example 1:
# Input:
# Players table:
# +-----------+-------------+
# | player_id | player_name |
# +-----------+-------------+
# | 1         | Nadal       |
# | 2         | Federer     |
# | 3         | Novak       |
# +-----------+-------------+
# Championships table:
# +------+-----------+---------+---------+---------+
# | year | Wimbledon | Fr_open | US_open | Au_open |
# +------+-----------+---------+---------+---------+
# | 2018 | 1         | 1       | 1       | 1       |
# | 2019 | 1         | 1       | 2       | 2       |
# | 2020 | 2         | 1       | 2       | 2       |
# +------+-----------+---------+---------+---------+
# Output:
# +-----------+-------------+-------------------+
# | player_id | player_name | grand_slams_count |
# +-----------+-------------+-------------------+
# | 2         | Federer     | 5                 |
# | 1         | Nadal       | 7                 |
# +-----------+-------------+-------------------+
# Explanation:
# Player 1 (Nadal) won 7 titles: Wimbledon (2018, 2019), Fr_open (2018, 2019, 2020), US_open (2018), and Au_open (2018).
# Player 2 (Federer) won 5 titles: Wimbledon (2020), US_open (2019, 2020), and Au_open (2019, 2020).
# Player 3 (Novak) did not win anything, we did not include them in the result table.

import pandas as pd

def grand_slam_titles(players: pd.DataFrame, championships: pd.DataFrame) -> pd.DataFrame:
  melted = championships.melt(id_vars='year', value_vars=['Wimbledon', 'Fr_open', 'US_open', 'Au_open'],
                var_name='tournament', value_name='player_id')
  counts = melted.groupby('player_id').size().reset_index(name='grand_slams_count')
  result = counts.merge(players, on='player_id')
  return result[['player_id', 'player_name', 'grand_slams_count']]