title: ElasticSearch [term] query doesn't support multiple fields
body: <p>I have the following data structure in ElasticSearch:</p>
  
  <pre><code>"assets": {
       "type": "nested",
       "properties": {
           "assetId": {
               "type": "keyword"
           },
           "assetSource": {
               "type": "keyword"
           },
  }
  </code></pre>
  
  <p>Say I want to exclude the result that 'assetSource' has value 'Web'</p>
  
  <p>I used <code>Term(field='assets.assetSource', query='web')</code> in the <code>query.exclude</code>, but since assets is multi-field, it complains <code>[term] query doesn't support multiple fields</code></p>
  
  <p>How do I work around this problem?</p>