Add return None statement for when no data is found

cdplib/db_handlers/MongodbHandler.py

@@ -287,10 +287,16 @@ class MongodbHandler:
 
         except Exception as error:
             self._log.log_and_raise_error(('An error occured trying to query data from {}, with query {}: {}:{}. \nError:{}').format(collection_name, attribute, comparison_operator, attribute_value, error))
-        if return_as_dataframe:
-            return self.convert_mongo_data_into_dataframe(data, index, collection_name)
+            return None
+
+        if len(list(data))> 0:
+            if return_as_dataframe:
+                return self.convert_mongo_data_into_dataframe(data, index, collection_name)
+            else:
+                return data
         else:
-            return data
+            self._log.warning(('No data for the query was found').format())
+            return None
 
     def aggregate_data_and_generate_dataframe(self, collection_name: str, aggregation_pipeline: list, index: str = None):
 
@@ -298,6 +304,7 @@ class MongodbHandler:
             data = self._database[collection_name].aggregate(pipeline=aggregation_pipeline, allowDiskUse=True)
         except Exception as error:
             self._log.log_and_raise_error(('A problem occured when aggregating the collection {} with the pipeline {}. \nError: {}').format(collection_name, aggregation_pipeline, error))
+            return None
 
         return self.convert_mongo_data_into_dataframe(data, index, collection_name)
 
@@ -316,6 +323,7 @@ class MongodbHandler:
                 return df
             else:
                 self._log.warning(('No data for the query was found').format())
+                return None
         except Exception as error:
             self._log.log_and_raise_error(('An error occured trying to convert mongo data into pd.Dataframe. \nError: {} ').format(error))