def list_containers(self):
results = []<EOL>for image in self._bucket.list_blobs():<EOL><INDENT>if image.metadata is not None:<EOL><INDENT>if "<STR_LIT:type>" in image.metadata:<EOL><INDENT>if image.metadata['<STR_LIT:type>'] == "<STR_LIT>":<EOL><INDENT>results.append(image)<EOL><DEDENT><DEDENT><DEDENT><DEDENT>if len(results) == <NUM_LIT:0>:<EOL><INDENT>bot.info("<STR_LIT>")<EOL><DEDENT>return results<EOL>
return a list of containers, determined by finding the metadata field
       "type" with value "container." We alert the user to no containers 
       if results is empty, and exit

       {'metadata': {'items': 
                              [
                               {'key': 'type', 'value': 'container'}, ... 
                              ]
                    }
       }