title: How to access Django Model Fields from save_formset
body: <p>I have an Inline Model in Django model admin , and I need to create a condition before saving the items, here is the code am using : </p>
  
  <pre class="lang-py prettyprint-override"><code>class PRCItemInline(admin.TabularInline):
  
  
      def get_form(self, request, obj=None, **kwargs):
          form = super(PRCItemInline, self).get_form(request, obj, **kwargs)
          form.base_fields['product'].widget.attrs['style'] = 'width: 50px;'
          return form
  
      ordering = ['id']
      model = PRCItem
      extra = 1
      autocomplete_fields = [
          'product',
          'supplier',
      ]
  
      fields = (
          'product',  # 1
          'quantity',  # 2
          'unitary_value_reais_updated',  # 4
          'issuing_status',
          'approval_status',
          'receiving_status',
      )
      readonly_fields = ['issuing_status',
                         'approval_status',
                         'receiving_status',
                         ]
  
      def save_formset(self, request, form, formset, change):
          obj = form.instance
          if obj.purchase_request.is_analizer:
              return HttpResponse("You can't change this")
          else:
              obj.save()
  
  </code></pre>
  
  <p>As you see, I used the <code>save_formset</code> method to be able to reach the fields of the model, and then filter based on it. but it just saves the items no matter the If statement I added. </p>