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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_sessions(self, app_path):
        ''' Gets all currently active sessions for an application.

        Args:
            app_path (str) :
                The configured application path for the application to return
                sessions for.

        Returns:
            list[ServerSession]

        '''
        if app_path not in self._applications:
            raise ValueError("Application %s does not exist on this server" % app_path)
        return list(self._applications[app_path].sessions)