def METHOD_NAME(schemas):
    """Get max opset version among all schemas within each domain."""
    domain_opset_versions = dict()
    for domain_version_schema_map in schemas.values():
        for domain, version_schema_map in domain_version_schema_map.items():
            # version_schema_map is sorted by since_version in descend order
            max_version = next(iter(version_schema_map))
            if domain not in domain_opset_versions:
                domain_opset_versions[domain] = int(max_version)
            else:
                domain_opset_versions[domain] = max(domain_opset_versions[domain], int(max_version))
    return domain_opset_versions