with .get and using ()

[20:11:33]  <@frogor>	 justinrummel:   so self.env is a dictionary.
You can reference a dictionary's item by its key like:
dict_name[key_name]  - but if the key doesn't exist, you get an error
[20:11:37]  <@frogor>	 So for python dictionaries
[20:11:51]  <@frogor>	 If you instead query them with a different
method:   dict_name.get(key_name, alternate_value)
[20:12:03]  <@frogor>	 If the key doesn't exist, then the result isn't
an error - it's the alternate_value