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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 ensure_client(self, config_file=None, is_demo=False, proxy=None):
 """Create a new SLAPI client to the environment. This will be a no-op if there is already a client in this environment. """

        if self.client is not None:
            return

        # Environment can be passed in explicitly. This is used for testing
        if is_demo:
            client = SoftLayer.BaseClient(
                transport=SoftLayer.FixtureTransport(),
                auth=None,
            )
        else:
            # Create SL Client
            client = SoftLayer.create_client_from_env(
                proxy=proxy,
                config_file=config_file,
            )
        self.client = client