bpo-38738: Fix formatting of True and False. (GH-17083)

* "Return true/false" is replaced with "Return ``True``/``False``"
  if the function actually returns a bool.
* Fixed formatting of some True and False literals (now in monospace).
* Replaced "True/False" with "true/false" if it can be not only bool.
* Replaced some 1/0 with True/False if it corresponds the code.
* "Returns <bool>" is replaced with "Return <bool>".
diff --git a/Doc/library/xml.etree.elementtree.rst b/Doc/library/xml.etree.elementtree.rst
index abc15d4..658bc3a 100644
--- a/Doc/library/xml.etree.elementtree.rst
+++ b/Doc/library/xml.etree.elementtree.rst
@@ -586,8 +586,8 @@
 
 .. function:: iselement(element)
 
-   Checks if an object appears to be a valid element object.  *element* is an
-   element instance.  Returns a true value if this is an element object.
+   Check if an object appears to be a valid element object.  *element* is an
+   element instance.  Return ``True`` if this is an element object.
 
 
 .. function:: iterparse(source, events=None, parser=None)