python rewrite lfilter (iir) with for
from:

a[0]*y[n] = b[0]*x[n] + b[1]*x[n-1] + ... + b[M]*x[n-M]
                      - a[1]*y[n-1] - ... - a[N]*y[n-N]


rewrite to:

a=[0.1298]
b=[1,-.8702]

a[0] * y[n] = b[0] * x[n] + b[1] * x[n-1]

y[n] = ( 1 * x[n] + -.8702*x[n-1] )/.1298