def is_empty(self):
        """
        Return True if the module has no content and False otherwise.

        >>> mod = DashboardModule()
        >>> mod.is_empty()
        True
        >>> mod.pre_content = 'foo'
        >>> mod.is_empty()
        False
        >>> mod.pre_content = None
        >>> mod.is_empty()
        True
        >>> mod.children.append('foo')
        >>> mod.is_empty()
        False
        >>> mod.children = []
        >>> mod.is_empty()
        True
        """
        return self.pre_content is None and \
               self.post_content is None and \
               len(self.children) == 0