UserConfiguration.UserConfiguration C# (CSharp) Method

      public UserConfiguration()
      {
        ToTable("user");
        HasKey(x => x.UserId)
          .Property(x => x.UserId)
          .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
    
       HasMany(x => x.UserGroups)
         .WithRequired(x => x.User); 
    }