[common][mixins] Fix key search in dictionaries

beat/web/common/mixins.py

@@ -58,12 +58,12 @@ class SerializerFieldsMixin(object):
         fields = None
         query_params = request.query_params
 
-        if query_params.has_key('fields'):
+        if 'fields' in query_params:
             fields = query_params['fields'].split(',')
         else:
             fields = self.get_serializer_class().Meta.default_fields
 
-        if query_params.has_key('include_fields'):
+        if 'include_fields' in query_params:
             include_fields = query_params['include_fields'].split(',')
             fields.extend(include_fields)