title: OR operator in Flask-sqlachemy query
body: <p>I using flask-sqlachemy. It is an extension of sqlachemy and I am not sure how <code>_or</code> translates to flask-sqlalchemy. For example, my query:</p>
  <pre><code>qry = DateModel.query.filter(
              DateModel.from_date &gt;= f_date, 
              DateModel.from_date &lt;= t_date).all()
  </code></pre>
  <p>Here two lines inside filter translates to <code>AND</code>. So I get all records between <code>f_date</code> and <code>t_date</code>.</p>
  <p>Now I want to add more data with <code>OR</code>. For example:</p>
  <pre><code>qry = DateModel.query.filter(
              DateModel.from_date &gt;= f_date, 
              DateModel.from_date &lt;= t_date 
  
              OR?
  
              DateModel.to_date &gt;= f_date, 
              DateModel.to_date &lt;= t_date).all()
  </code></pre>
  <p>What would be the syntax for such query?</p>