Get an attribute of the holder (read-only access).

def get(self, name, strict=True):
        """Get an attribute of the holder (read-only access)."""
        if not isinstance(name, str) or name.startswith('_'):
            raise AttributeError(self.__class__.__name__, name)
        elif strict and name not in self._possible_attributes:
            raise AttributeError('%s is not a valid attribute of %r.' %
                                 (name, self))
        elif name in self._attributes:
            return self._attributes[name]
        else:
            raise exceptions.AttributeNotProvided(name)