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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 project_run_path(cls, project, transfer_config, run):
 """Return a fully-qualified project_run string."""

        return google.api_core.path_template.expand(
            "projects/{project}/transferConfigs/{transfer_config}/runs/{run}",
            project=project,
            transfer_config=transfer_config,
            run=run,
        )