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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 _determine_hpp_url(self, platform, action):
 """This returns the Adyen HPP endpoint based on the provided platform, and action. Args: platform (str):
 Adyen platform, ie 'live' or 'test'. action (str):
 the HPP action to perform. possible actions: select, pay, skipDetails, directory """

        base_uri = settings.BASE_HPP_URL.format(platform)
        service = action + '.shtml'
        result = '/'.join([base_uri, service])
        return result