[examples] comments.

bonobo/examples/environ.py

@@ -1,26 +1,26 @@
+"""
+This transformation extracts the environment and prints it, sorted alphabetically, one item per line.
+
+Used in the bonobo tests around environment management.
+
+"""
 import os
 
 import bonobo
 
 
 def extract_environ():
+    """Yield all the system environment."""
     yield from sorted(os.environ.items())
 
 
 def get_graph():
-    """
-    This function builds the graph that needs to be executed.
-
-    :return: bonobo.Graph
-
-    """
     graph = bonobo.Graph()
     graph.add_chain(extract_environ, print)
 
     return graph
 
 
-# The __main__ block actually execute the graph.
 if __name__ == '__main__':
     parser = bonobo.get_argument_parser()
     with bonobo.parse_args(parser):