Add a help message so it is more obvious what this script does:
Add a help message so it is more obvious what this script does:

Generate dx.pickle, dy.pickle distortion maps for a detector model picked up
from either an image file or a datablock.json. These maps can be used to
represent distortion within the millimetre to pixel mapping

Examples:

  dials.generate_distortion_maps image_001.cbf dx=0.5 dy=1.5
  dials.generate_distortion_maps datablock.json mode=ellipse phi=0 l2=0.95

dials/dials,dials/dials,dials/dials,dials/dials,dials/dials