def METHOD_NAME(handler: "SMIRNOFFVirtualSiteCollection"):
    _SUPPORTED_EXCLUSION_POLICIES = ("parents",)
    if handler.exclusion_policy not in _SUPPORTED_EXCLUSION_POLICIES:
        raise UnsupportedExportError(
            f"Found unsupported exclusion policy {handler.exclusion_policy}. "
            f"Supported exclusion policies are {_SUPPORTED_EXCLUSION_POLICIES}",
        )