  skipna : bool, default True
            Flag to ignore nan values during truth testing.

        Returns
        -------
        Series or DataFrame
            DataFrame or Series of boolean values, where a value is True if all elements
            are True within its respective group, False otherwise.
        %(see_also)s
        Examples
        --------

        For SeriesGroupBy:

        >>> lst = ['a', 'a', 'b']
        >>> ser = pd.Series([1, 2, 0], index=lst)
        >>> ser
        a    1
        a    2
        b    0
        dtype: int64
        >>> ser.groupby(level=0).all()
        a     True
        b    False
        dtype: bool

        For DataFrameGroupBy:

        >>> data = [[1, 0, 3], [1, 5, 6], [7, 8, 9]]
        >>> df = pd.DataFrame(data, columns=["a", "b", "c"],
        ...                   index=["ostrich", "penguin", "parrot"])
        >>> df
                 a  b  c
        ostrich  1  0  3
        penguin  1  5  6
        parrot   7  8  9
        >>> df.groupby(by=["a"]).all()
               b      c
        a
        1  False   True
        7   True   True
        rn