❔ Serializing related object EF

public class City {
    [Key]
    public int Id { get; set; }
    [Required]
    public string Name { get; set; }
    [Required]
    public string CountryName { get; set; }
    public Coordinates? Coordinates { get; set; }
}

public class Coordinates {
    public int Id { get; set; }
    public double X { get; set; }
    public double Y { get; set; }
    public int CityId { get; set; }
    public City City { get; set; } = null!;
}

return db.Cities
        .Where(c => c.Name.ToLower().Contains(city.ToLower()))
        .Include(c => c.Coordinates)
        .ToList();