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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 _injectWorkerFiles(self, node, botoExists):
 """ Set up the credentials on the worker. """

        node.waitForNode('toil_worker', keyName=self._keyName)
        node.copySshKeys(self._keyName)
        node.injectFile(self._credentialsPath, GoogleJobStore.nodeServiceAccountJson, 'toil_worker')
        if self._sseKey:
            node.injectFile(self._sseKey, self._sseKey, 'toil_worker')
        if botoExists:
            node.injectFile(self._botoPath, self.NODE_BOTO_PATH, 'toil_worker')