step_detect: Update a docstring
step_detect: Update a docstring

qwhelan/asv,airspeed-velocity/asv,spacetelescope/asv,pv/asv,airspeed-velocity/asv,pv/asv,airspeed-velocity/asv,spacetelescope/asv,pv/asv,qwhelan/asv,spacetelescope/asv,pv/asv,spacetelescope/asv,qwhelan/asv,airspeed-velocity/asv,qwhelan/asv