def method(self, foo=None, bar=None):
pass<EOL>
A sample DataFrame method.

Do not import numpy and pandas.

Try to use meaningful data, when it makes the example easier
to understand.

Try to avoid positional arguments like in `df.method(1)`. They
can be alright if previously defined with a meaningful name,
like in `present_value(interest_rate)`, but avoid them otherwise.

When presenting the behavior with different parameters, do not place
all the calls one next to the other. Instead, add a short sentence
explaining what the example shows.

Examples
--------
>>> import numpy as np
>>> import pandas as pd
>>> df = pd.DataFrame(np.ones((3, 3)),
...                   columns=('a', 'b', 'c'))
>>> df.all(1)
0    True
1    True
2    True
dtype: bool
>>> df.all(bool_only=True)
Series([], dtype: bool)