title: Django Validation with and or rule
body: <p>The condition supposed to be only if this field is filled other field do not need to filled. Now with this code i have to fill out all the fields.</p>
  <pre><code> if (self.start==None and self.end==None) or (self.running==None  and self.walking==None ) :
          raise ValidationError(
              {
                  &quot;start&quot;: _(&quot;Need to be filled&quot;),
                   &quot;end&quot;: _(&quot;Need to be filled&quot;),
                  &quot;running&quot;: _(&quot;Need to be filled&quot;),
                  &quot;walking&quot;: _(&quot;Need to be filled&quot;)
              }
          )
  </code></pre>