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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_dm_channel(self, userid):
        '''Perform a lookup of users to resolve a userid to a DM channel

        Args:
            userid (string): Slack userid to lookup.

        Returns:
            string: DM channel ID of user
        '''

        dm_open = self.slack_client.api_call('im.open', user=userid)
        return dm_open['channel']['id']