I have few form fields on search page. After performing the search, my page should display a list of possible matching results. If the user typed in only part of a title, ISBN, or author name, search page should find matches for those as well. Also if user typed only one or few field - page should show all matches.

Idk how to write query. If i have one value from request.form and other values is None - so whole query is empty

```
@app.route('/search', methods=("GET", "POST"))
def search_book():
    books = None
    if request.method == "POST":
        isbn = request.form['isbn']
        title = request.form['title']
        author = request.form['author']
        year = request.form['year']
        books = db.query(Books).filter_by(isbn=isbn, title=title, author=author, year=year).all()
    return render_template("search.html", books=books)

```