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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 tag_path(cls, project, incident, tag):
 """Return a fully-qualified tag string."""

        return google.api_core.path_template.expand(
            "projects/{project}/incidents/{incident}/tags/{tag}",
            project=project,
            incident=incident,
            tag=tag,
        )