def _get_window(self, other=None):
axis = self.obj._get_axis(self.axis)<EOL>length = len(axis) + (other is not None) * len(axis)<EOL>other = self.min_periods or -<NUM_LIT:1><EOL>return max(length, other)<EOL>
Get the window length over which to perform some operation.

Parameters
----------
other : object, default None
    The other object that is involved in the operation.
    Such an object is involved for operations like covariance.

Returns
-------
window : int
    The window length.