test whether variance is the same in 2 subsamples
Parameters:  y : array_like
x : array_like
idx : integer
split : None or integer or float in intervall (0,1)
drop : None, float or int
alternative : string, ‘increasing’, ‘decreasing’ or ‘twosided’


Returns:  (fval, pval) or res : fval : float
pval : float
res : instance of result class

Notes
The Null hypothesis is that the variance in the two subsamples are the same. The alternative hypothesis, can be increasing, i.e. the variance in the second sample is larger than in the first, or decreasing or twosided.
Results are identical R, but the drop option is defined differently. (sorting by idx not tested yet)
Methods
run(y, x[, idx, split, drop, alternative, ...])  see class docstring 