Copy-edit the docstring of AuxTransformBox.

It can like be made even clearer; here I tried to just repeat what
was written but with a clearer style.

Some minor additional edits are included as well.

Author: anntzer

lib/matplotlib/offsetbox.py

@@ -201,7 +201,7 @@ def _get_aligned_offsets(yspans, height, align="baseline"):
 
 class OffsetBox(martist.Artist):
     """
-    The OffsetBox is a simple container artist.
+    A simple container artist.
 
     The child artists are meant to be drawn at a relative position to its
     parent.
@@ -826,17 +826,18 @@ def draw(self, renderer):
 
 class AuxTransformBox(OffsetBox):
     """
-    Offset Box with the aux_transform. Its children will be
-    transformed with the aux_transform first then will be
-    offsetted. The absolute coordinate of the aux_transform is meaning
-    as it will be automatically adjust so that the left-lower corner
-    of the bounding box of children will be set to (0, 0) before the
-    offset transform.
-
-    It is similar to drawing area, except that the extent of the box
-    is not predetermined but calculated from the window extent of its
-    children. Furthermore, the extent of the children will be
-    calculated in the transformed coordinate.
+    An OffsetBox with an auxiliary transform.
+
+    All child artists are first transformed with *aux_transform*, then
+    translated with an offset (the same for all children) so the bounding
+    box of the children matches the drawn box.  (In other words, adding an
+    arbitrary translation to *aux_transform* has no effect as it will be
+    cancelled out by the later offsetting.)
+
+    `AuxTransformBox` is similar to `.DrawingArea`, except that the extent of
+    the box is not predetermined but calculated from the window extent of its
+    children, and the extent of the children will be calculated in the
+    transformed coordinate.
     """
     def __init__(self, aux_transform):
         self.aux_transform = aux_transform
@@ -853,10 +854,7 @@ def add_artist(self, a):
         self.stale = True
 
     def get_transform(self):
-        """
-        Return the :class:`~matplotlib.transforms.Transform` applied
-        to the children
-        """
+        """Return the `.Transform` applied to the children."""
         return (self.aux_transform
                 + self.ref_offset_transform
                 + self.offset_transform)
@@ -908,7 +906,7 @@ def draw(self, renderer):
 
 class AnchoredOffsetbox(OffsetBox):
     """
-    An offset box placed according to location *loc*.
+    An OffsetBox placed according to location *loc*.
 
     AnchoredOffsetbox has a single child.  When multiple children are needed,
     use an extra OffsetBox to enclose them.  By default, the offset box is