[loggingTools] add docstring to exemplify usage of LogMixin

Lib/fontTools/misc/loggingTools.py

@@ -473,8 +473,29 @@ class CapturingLogHandler(logging.Handler):
 
 
 class LogMixin(object):
-	""" Mixin class that adds a 'log' property getter returning an instance
-	of logging.Logger class, which is named after self <module>.<class> name.
+	""" Mixin class that adds logging functionality to another class.
+	You can define a new class that subclasses from LogMixin as well as
+	other base classes through multiple inheritance.
+	All instances of that class will have a 'log' property that returns
+	a logging.Logger named after their respective <module>.<class>.
+	For example:
+
+	>>> class BaseClass(object):
+	...     pass
+	>>> class MyClass(LogMixin, BaseClass):
+	...     pass
+	>>> a = MyClass()
+	>>> isinstance(a.log, logging.Logger)
+	True
+	>>> print(a.log.name)
+	fontTools.misc.loggingTools.MyClass
+	>>> class AnotherClass(MyClass):
+	...     pass
+	>>> b = AnotherClass()
+	>>> isinstance(b.log, logging.Logger)
+	True
+	>>> print(b.log.name)
+	fontTools.misc.loggingTools.AnotherClass
 	"""
 
 	@property