"query malformed, must start with start_object" exception when deleting by query

[Perlence]

Hello,

I'm trying to delete documents by query:

>>> import pyes
>>> es = pyes.ES('http://localhost:9200')
>>> es.delete_by_query(['social'], ['post'], pyes.TermQuery('source_id', 38))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/ubuntu/Workspace/social/crawlers/env/local/lib/python2.7/site-packages/pyes/es.py", line 909, in delete_by_query
    return self._send_request('DELETE', path, body, query_params)
  File "/home/ubuntu/Workspace/social/crawlers/env/local/lib/python2.7/site-packages/pyes/es.py", line 470, in _send_request
    raise_if_error(response.status, decoded)
  File "/home/ubuntu/Workspace/social/crawlers/env/local/lib/python2.7/site-packages/pyes/convert_errors.py", line 67, in raise_if_error
    result, request)
pyes.exceptions.ElasticSearchException: Unknown exception type: 400, {'_indices': {'social': {'_shards': {'successful': 0, 'failed': 5, 'total': 5, 'failures': [{'index': 'social', 'reason': 'QueryParsingException[[social] [_na] query malformed, must start with start_object]', 'shard': 2}, {'index': 'social', 'reason': 'QueryParsingException[[social] [_na] query malformed, must start with start_object]', 'shard': 0}, {'index': 'social', 'reason': 'QueryParsingException[[social] [_na] query malformed, must start with start_object]', 'shard': 3}, {'index': 'social', 'reason': 'QueryParsingException[[social] [_na] query malformed, must start with start_object]', 'shard': 4}, {'index': 'social', 'reason': 'QueryParsingException[[social] [_na] query malformed, must start with start_object]', 'shard': 1}]}}}}

Post mapping is:

{
  "social": {
    "mappings": {
      "post": {
        "properties": {
          "comment_count": {
            "type": "integer"
          },
          "created_time": {
            "type": "date",
            "format": "dateOptionalTime"
          },
          "dislike_count": {
            "type": "integer"
          },
          "duration": {
            "type": "string",
            "index": "not_analyzed"
          },
          "favorite_count": {
            "type": "integer"
          },
          "like_count": {
            "type": "integer"
          },
          "link": {
            "type": "string",
            "index": "not_analyzed"
          },
          "location": {
            "type": "double"
          },
          "repost_count": {
            "type": "integer"
          },
          "social": {
            "type": "string",
            "index": "not_analyzed"
          },
          "source_id": {
            "type": "integer"
          },
          "text": {
            "type": "string"
          },
          "thumbnail": {
            "type": "string",
            "index": "not_analyzed"
          },
          "title": {
            "type": "string"
          },
          "user": {
            "type": "nested",
            "properties": {
              "bio": {
                "type": "string"
              },
              "created_time": {
                "type": "date",
                "format": "dateOptionalTime"
              },
              "first_name": {
                "type": "string",
                "index": "not_analyzed"
              },
              "full_name": {
                "type": "string",
                "index": "not_analyzed"
              },
              "gender": {
                "type": "string",
                "index": "not_analyzed"
              },
              "id": {
                "type": "string",
                "index": "not_analyzed"
              },
              "last_name": {
                "type": "string",
                "index": "not_analyzed"
              },
              "link": {
                "type": "string",
                "index": "not_analyzed"
              },
              "location": {
                "type": "string",
                "index": "not_analyzed"
              },
              "picture": {
                "type": "string",
                "index": "not_analyzed"
              },
              "username": {
                "type": "string",
                "index": "not_analyzed"
              },
              "website": {
                "type": "string",
                "index": "not_analyzed"
              }
            }
          },
          "view_count": {
            "type": "integer"
          }
        }
      }
    }
  }
}

Example post:

{
    "comment_count": 238,
    "created_time": "2014-04-21 14:17:50",
    "like_count": 925,
    "link": "...",
    "repost_count": 87,
    "social": "...",
    "source_id": 38,
    "text": "...",
    "thumbnail": "...",
    "user": {
        "full_name": "...",
        "id": "...",
        "link": "...",
        "username": "..."
    }
}