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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 get_main_activities(self):
 """ Return names of the main activities These values are read from the AndroidManifest.xml :rtype: a set of str """

        x = set()
        y = set()

        for i in self.xml:
            if self.xml[i] is None:
                continue
            activities_and_aliases = self.xml[i].findall(".//activity") + \
                                     self.xml[i].findall(".//activity-alias")

            for item in activities_and_aliases:
                # Some applications have more than one MAIN activity.
                # For example: paid and free content
                activityEnabled = item.get(self._ns("enabled"))
                if activityEnabled == "false":
                    continue

                for sitem in item.findall(".//action"):
                    val = sitem.get(self._ns("name"))
                    if val == "android.intent.action.MAIN":
                        activity = item.get(self._ns("name"))
                        if activity is not None:
                            x.add(item.get(self._ns("name")))
                        else:
                            log.warning('Main activity without name')

                for sitem in item.findall(".//category"):
                    val = sitem.get(self._ns("name"))
                    if val == "android.intent.category.LAUNCHER":
                        activity = item.get(self._ns("name"))
                        if activity is not None:
                            y.add(item.get(self._ns("name")))
                        else:
                            log.warning('Launcher activity without name')

        return x.intersection(y)