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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 getCSS(self):
 """ Returns the css style to be used for the current template. If the selected template is 'default.pt', this method will return the content from 'default.css'. If no css file found for the current template, returns empty string """

        template = self.request.get('template', self._DEFAULT_TEMPLATE)
        content = ''
        if template.find(':') >= 0:
            prefix, template = template.split(':')
            resource = queryResourceDirectory(
                self._TEMPLATES_ADDON_DIR, prefix)
            css = '{0}.css'.format(template[:-3])
            if css in resource.listDirectory():
                content = resource.readFile(css)
        else:
            this_dir = os.path.dirname(os.path.abspath(__file__))
            templates_dir = os.path.join(this_dir, self._TEMPLATES_DIR)
            path = '%s/%s.css' % (templates_dir, template[:-3])
            with open(path, 'r') as content_file:
                content = content_file.read()
        return content