diff --git a/mglib/step.py b/mglib/step.py
index f6b645e..2d8b344 100644
--- a/mglib/step.py
+++ b/mglib/step.py
@@ -2,26 +2,27 @@ class Step:
     # Q: What is ``Step`` and why it was a bad decision to introduce it?
     #
     # A: ``Step`` class is closely related to zooming in/zooming out
-    # a specific page in the document in the front-end (javascript code). 
+    # a specific page in the document in the frontend (javascript code).
+    #
     # When user opens the document in document viewer, he/she actually
     # sees an image with text over it (text overlay). Text overlay is
     # created from hocr data. Very important point here, is that
     # text hocr data corresponds to (extracted, format jpeg) image of the page
     # of VERY SAME width/height. Again, hocr file and respective image file
     # of the page MUST HAVE SAME WIDTH AND HEIGHT.
-    # 
+    #
     # Each step is meant to be a specific zoom value of the page. Thus, step
     # 2, which corresonds to LIST[2] % = 75 % of the page initial logical size
     # of WIDTH_100p = 1240.
-    # When user zooms in/zooms out - a new hocr file is downloaded corresponding
-    # to that zoom step. As you may guess, user can zoom only 125%, 100%, 75%
-    # and 50%. Value of 10% corresponds to thumbnail of the document and does
-    # not count as 'real' step.
-    # 
+    # When user zooms in/zooms out - a new hocr file is downloaded
+    # corresponding to that zoom step. As you may guess, user can zoom only
+    # 125%, 100%, 75% and 50%. Value of 10% corresponds to thumbnail of the
+    # document and does not count as 'real' step.
+    #
     # Instead of doing this step thingy, it would have been better to drop
     # the entire step concept. Much better solution for zoom in/zoom out would
-    # have been to download one SVG file for each page (instead of hocr) and 
-    # SVG file of respective page should contain embedded image 
+    # have been to download one SVG file for each page (instead of hocr) and
+    # SVG file of respective page should contain embedded image
     # (binary jpeg; yes SVG format allows embedding of binary formats!) and
     # correctly mapped text overlay (built from hocr file). User later
     #  can zoom in/zoom out using SVG transforations in frontend!
@@ -30,13 +31,13 @@ class Step:
     #
     # * there will be 4X less OCR required (corresponding to
     #     hOCR of each step minus thumbnail/10% step)
-    # * will simplify front-end code as SVG (= hocr + jpeg) will be generated on
-    #      on server side 
-    # * eliminate conept of Step entirely 
+    # * will simplify front-end code as SVG (= hocr + jpeg) will be
+    #       generated on the on server side
+    # * eliminate conept of Step entirely
     #    (there will be only one SVG file per page)
     # * increase front-end and back-end performance as only one file SVG file
     #   will be sent back and forth (from backend to frontend)
-    # 
+    #
     # width of a document when displayed as 100%.
     WIDTH_100p = 1240
     PERCENT = 100