Fix chaining of fetch methods

Change-Id: I344bd4697a5a28bae6149063a7cb67c22b0a589a
diff --git a/KorAPClient/__init__.py b/KorAPClient/__init__.py
index 35c4c3a..82f0501 100644
--- a/KorAPClient/__init__.py
+++ b/KorAPClient/__init__.py
@@ -312,7 +312,8 @@
         with localconverter(fix_lists_in_dataframes):
             df = res.slots['collectedMatches']
         res.slots['collectedMatches'] = df
-        return res
+        super().__init__(res)
+        return self
 
     def fetchRest(self, *args, **kwargs):
         """Fetch remaining query results
@@ -326,7 +327,8 @@
         with localconverter(fix_lists_in_dataframes):
             df = res.slots['collectedMatches']
         res.slots['collectedMatches'] = df
-        return res
+        super().__init__(res)
+        return self
 
     def fetchAll(self, *args, **kwargs):
         """Fetch all query results
@@ -343,5 +345,6 @@
         with localconverter(fix_lists_in_dataframes):
             df = res.slots['collectedMatches']
         res.slots['collectedMatches'] = df
-        return res
+        super().__init__(res)
+        return self