code: def expand(self, name):
          
          if self._is_pattern(name):
              expr = re.compile(self._pattern_to_regex(name))
              for cfg_name in self._d.keys():
                  if expr.match(cfg_name):
                      self._expand(cfg_name)
          else:
              self._expand(name)
docs: Expand config for `name` by adding a sub-configuration for every
          dot-separated collection "below" the given one (or all, if none given).
  
          For example, for a database 'mydb' with collections
              ['spiderman.amazing', 'spiderman.spectacular', 'spiderman2']
          and a configuration
              {'host':'foo', 'database':'mydb', 'collection':'spiderman'}
          then `expand("mydb.spiderman")` would add keys for 'spiderman.amazing'
          and 'spiderman.spectacular', but *not* 'spiderman2'.
  
          :param name: Name, or glob-style pattern, for DB configurations.
          :type name: basestring
          :return: None
          :raises: KeyError (if no such configuration)