code: def fetch(self, collection, **kwargs):
          '''
          return one record from the collection whose parameters match kwargs
          ---
          kwargs should be a dictionary whose keys match column names (in
          traditional SQL / fields in NoSQL) and whose values are the values of
          those fields.
          e.g. kwargs={name='my application name',client_id=12345}
          '''
          callback = kwargs.pop('callback')
          data = yield Op(self.db[collection].find_one, kwargs)
          callback(dataf fetch(self, collection, **kwargs):
          '''
          return one record from the collection whose parameters match kwargs
          ---
          kwargs should be a dictionary whose keys match column names (in
          traditional SQL / fields in NoSQL) and whose values are the values of
          those fields.
          e.g. kwargs={name='my application name',client_id=12345}
          '''
          callback = kwargs.pop('callback')
          data = yield Op(self.db[collection].find_one, kwargs)
          callback(data)
docs: return one record from the collection whose parameters match kwargs
          ---
          kwargs should be a dictionary whose keys match column names (in
          traditional SQL / fields in NoSQL) and whose values are the values of
          those fields.
          e.g. kwargs={name='my application name',client_id=12345}