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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def render_css_classes(self):
 """ Return a string containing the css classes for the module. 'dashboard-module disabled draggable collapsible deletable' 'dashboard-module disabled draggable collapsible deletable foo' 'dashboard-module draggable collapsible deletable foo' """

        ret = ['dashboard-module']
        if not self.enabled:
            ret.append('disabled')
        if self.draggable:
            ret.append('draggable')
        if self.collapsible:
            ret.append('collapsible')
        if self.deletable:
            ret.append('deletable')
        ret += self.css_classes
        return ' '.join(ret)