title: django-import-export how to deal with the import_id_fields is unique_together key?
body: <p>the parentmodel is</p>
  <pre><code>class Work(models.Model):
      po = models.ForeignKey(Po, verbose_name=&quot;合同号&quot;, on_delete=models.CASCADE)
      remark = models.CharField(max_length=100, verbose_name=&quot;备注说明&quot;)
      create_time=models.DateField(verbose_name=&quot;日期&quot;)
  
      class Meta:
          verbose_name = &quot;工作清单&quot;
          verbose_name_plural = verbose_name
          unique_together=(&quot;po&quot;,&quot;remark&quot;)
  
      def __str__(self):
          return self.remark
  </code></pre>
  <p>and the children model is</p>
  <pre><code>class Acceptance(models.Model):
      work = models.ForeignKey(Work, on_delete=models.CASCADE, verbose_name=&quot;工作清单&quot;)
      detail=models.ForeignKey(Detail,on_delete=models.CASCADE,verbose_name=&quot;验收物品&quot;)
      accecpt_time = models.DateField(verbose_name=&quot;验收日期&quot;)
      num = models.IntegerField(verbose_name=&quot;验收数量&quot;, validators=[MinValueValidator(1)])
      person = models.CharField(max_length=100, verbose_name=&quot;验收人员&quot;)
      class Meta:
          verbose_name = &quot;验收清单&quot;
          verbose_name_plural = verbose_name
          unique_together=(&quot;accecpt_time&quot;,&quot;work&quot;)
  </code></pre>
  <p>I want to ask about how to defind the Acceptance Resource when the work foreign_key is unique_together key?
  my test code is</p>
  <pre><code>class AcceptanceSource(resources.ModelResource):
      work = fields.Field(attribute=&quot;work&quot;, widget=ForeignKeyWidget(Work, 'remark'), column_name=&quot;工作清单&quot;)
      detail = fields.Field(attribute=&quot;detail&quot;, widget=ForeignKeyWidget(Detail, &quot;name&quot;), column_name=&quot;物料清单&quot;)
      po = fields.Field(attribute=&quot;work__po&quot;, column_name=&quot;合同号&quot;, widget=ForeignKeyWidget(Po, &quot;po_num&quot;))
      num = fields.Field(attribute=&quot;num&quot;, column_name=&quot;验收数量&quot;)
      accecpt_time = fields.Field(attribute=&quot;accecpt_time&quot;, column_name=&quot;验收时间&quot;)
      person = fields.Field(attribute=&quot;person&quot;, column_name=&quot;验收人员&quot;)
  </code></pre>
  <p>but it get error like this:</p>
  <blockquote>
  <p>行号: 1 - get() returned more than one Work -- it returned 2!</p>
  </blockquote>