Bad Performance with querying database

Hi, I have document with bad performance. I used some profiler
and you can see result

Tue Apr  4 13:02:36 2017    /tmp/profile.pstat

         2399000 function calls (2399641 primitive calls) in 4.152 seconds

   Ordered by: internal time
   List reduced from 148 to 100 due to restriction <100>


   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
  104/704    2.225    0.021    7.144    0.010 /env/local/lib/python2.7/site-packages/mongoengine/base/fields.py:233(ListField.to_python)
  2379676    1.854    0.000    2.460    0.000 /env/local/lib/python2.7/site-packages/mongoengine/fields.py:62(StringField.to_python)
     8/40    0.031    0.004    7.180    0.179 /env/local/lib/python2.7/site-packages/mongoengine/base/document.py:539(_from_son)
        1    0.007    0.007    7.305    7.305 /env/local/lib/python2.7/site-packages/mongoengine/queryset/queryset.py:83(QuerySet._populate_cache)

I use pymongo for same query and load in 0.3 sec
what is problem?

Start with the profiler output and the MongoEngine paths it names: mongoengine/base/fields.py, mongoengine/fields.py, mongoengine/base/document.py, and mongoengine/queryset/queryset.py. Compare the MongoEngine query with the reported PyMongo 0.3-second result; a useful outcome would identify the cause and define a concrete performance change, but this issue does not specify an expected fix or test.