Using EF Include() with generic repository

gistfile1.cs

public IQueryable<T> FindBy(Expression<Func<T, bool>> predicate, params Expression<Func<T, object>>[] includes)
{
    var query = GetAll().Where(predicate);
    return includes.Aggregate(query, (current, includeProperty) => current.Include(includeProperty));
}

// Sample usage
userRepository.FindBy(x => x.Username == username, x.Roles)

I get error near GetAll(), as shown in the figure

This is my GetAll () Method
public virtual IEnumerable GetAll()
{
return DbSet.ToList();
}

public async Task<IEnumerable> FindBy(Expression<Func<TEntity, bool>> filter, Func<IQueryable, IOrderedQueryable> orderBy = null, params Expression<Func<TEntity, object>>[] includes)
{
try
{
IQueryable query = this.DbSet.Where(filter);
if (orderBy != null)
query = orderBy(query);
includes.Aggregate(query, (current, includeProperty) => current.Include(includeProperty));
return await query.ToListAsync();
}
catch (Exception e)
{
throw e;
}
}

How can I use ThenInclude with this?
I have User class which contains ICollection<Skill>, where every Skill instance contains ICollection<Entry>.
FindBy(x => x.Id == 1, x.Skills) works perfect, but how include Entries in every Skill?

They do it here https://github.com/digipolisantwerp/dataaccess_aspnetcore

You can "_context.Set()" instead of GetAll() who have error.
Nice solution thank you ...

public IQueryable Find(Expression<Func<T, bool>> predicate, params Func<IQueryable, IQueryable>[] includes) =>
includes.Aggregate(_dbContext.Set().Where(predicate).AsQueryable(), (current, includesproptity) => includesproptity(current));

_context.Find(a => a.id == id, image =>
{
return image.Include(b => b.PersonImages)
.ThenInclude(a => a.Image);
}, personType =>
{
return personType.Include(a => a.PersonType);
});

Sample usage is wrong should be like this:

// Sample usage
userRepository.FindBy(x => x.Username == username, x=> x.Roles)

How Can I get multiple navigation property