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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 file_client(self):
        '''
        Return a file client. Instantiates on first call.
        '''
        if not self._file_client:
            self._file_client = salt.fileclient.get_file_client(
                self.opts, self.pillar_rend)
        return self._file_client