Q rings, q indices, number of pixels in each q ring

This module will compute the Q values for all pixels in a shape specified by
detector_size and find the indices of the required Q rings. Count the
number of pixels in each Q ring.
Yes but first time (line 160)
q_inds, q_ring_val, num_pixels = recip.q_rings(num_qs, first_q, delta_q, q_val) without step_q  but 
in (line 189) again that function calls with step_q