"""
* Assignment: DataFrame Groupby Astro Flights
* Complexity: medium
* Lines of code: 5 lines
* Time: 13 min

English:
    1. Read data from `DATA` as `df: pd.DataFrame`
    2. Create ranking of the most experienced astronauts (number of flights)
    3. Run doctests - all must succeed

Polish:
    1. Wczytaj dane z `DATA` jako `df: pd.DataFrame`
    2. Stwórz ranking najbardziej doświadczonych astronautów (liczba lotów)
    3. Uruchom doctesty - wszystkie muszą się powieść

Tests:
    >>> import sys; sys.tracebacklimit = 0

    >>> pd.set_option('display.width', 500)
    >>> pd.set_option('display.max_columns', 10)
    >>> pd.set_option('display.max_rows', 10)

    # >>> assert result is not Ellipsis, \
    # 'Assign result to variable: `result`'
    # >>> assert type(result) is pd.DataFrame, \
    # 'Variable `result` must be a `pd.DataFrame` type'

    >>> result  # doctest: +NORMALIZE_WHITESPACE
    Ellipsis

TODO: Doctests
"""

import pandas as pd


# type: pd.DataFrame
result = ...


# Solution