Constructs form from POST method using self.form_class.

def construct_form(self, request):
        """
        Constructs form from POST method using self.form_class.
        """
        if not hasattr(self, 'form_class'):
            return None

        if request.method == 'POST':
            form = self.form_class(self.model, request.POST, request.FILES)
        else:
            form = self.form_class(self.model)
        return form