From d6aa01db18739aea43177cfcec41f8667aebdb3d Mon Sep 17 00:00:00 2001
From: shreyasnagare <shreyasnagare@gmail.com>
Date: Wed, 30 Jun 2021 03:27:26 -0400
Subject: [PATCH 1/4] Update graph operator overloading for subclasses

---
 rdflib/graph.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/rdflib/graph.py b/rdflib/graph.py
index f90b3acbb..c354a7705 100644
--- a/rdflib/graph.py
+++ b/rdflib/graph.py
@@ -558,7 +558,7 @@ def __isub__(self, other):
     def __add__(self, other):
         """Set-theoretic union
            BNode IDs are not changed."""
-        retval = Graph()
+        retval = self.__class__()
         for (prefix, uri) in set(list(self.namespaces()) + list(other.namespaces())):
             retval.bind(prefix, uri)
         for x in self:
@@ -570,7 +570,7 @@ def __add__(self, other):
     def __mul__(self, other):
         """Set-theoretic intersection.
            BNode IDs are not changed."""
-        retval = Graph()
+        retval = self.__class__()
         for x in other:
             if x in self:
                 retval.add(x)
@@ -579,7 +579,7 @@ def __mul__(self, other):
     def __sub__(self, other):
         """Set-theoretic difference.
            BNode IDs are not changed."""
-        retval = Graph()
+        retval = self.__class__()
         for x in self:
             if x not in other:
                 retval.add(x)

From 529caa24feca237ae31b84adabb7c90c2805ba83 Mon Sep 17 00:00:00 2001
From: shreyasnagare <shreyasnagare@gmail.com>
Date: Wed, 30 Jun 2021 19:33:17 -0400
Subject: [PATCH 2/4] Add tests for operators

---
 test/test_graph_operator.py | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 test/test_graph_operator.py

diff --git a/test/test_graph_operator.py b/test/test_graph_operator.py
new file mode 100644
index 000000000..87502c54b
--- /dev/null
+++ b/test/test_graph_operator.py
@@ -0,0 +1,27 @@
+from rdflib import Graph
+
+
+class MyGraph(Graph):
+    def my_method(self):
+        pass
+
+
+def test_subclass_add_operator():
+    g = MyGraph()
+
+    g = g + g
+    assert "my_method" in dir(g)
+
+
+def test_subclass_sub_operator():
+    g = MyGraph()
+
+    g = g - g
+    assert "my_method" in dir(g)
+
+
+def test_subclass_mul_operator():
+    g = MyGraph()
+
+    g = g * g
+    assert "my_method" in dir(g)

From db531bf65a7780204d670387affdb5d14fcd4d91 Mon Sep 17 00:00:00 2001
From: shreyasnagare <shreyasnagare@gmail.com>
Date: Wed, 30 Jun 2021 19:35:08 -0400
Subject: [PATCH 3/4] Add fallback for subclasses with required init args

---
 rdflib/graph.py | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/rdflib/graph.py b/rdflib/graph.py
index c354a7705..8cbc066d2 100644
--- a/rdflib/graph.py
+++ b/rdflib/graph.py
@@ -558,7 +558,10 @@ def __isub__(self, other):
     def __add__(self, other):
         """Set-theoretic union
            BNode IDs are not changed."""
-        retval = self.__class__()
+        try:
+            retval = self.__class__()
+        except TypeError:
+            retval = Graph()
         for (prefix, uri) in set(list(self.namespaces()) + list(other.namespaces())):
             retval.bind(prefix, uri)
         for x in self:
@@ -570,7 +573,10 @@ def __add__(self, other):
     def __mul__(self, other):
         """Set-theoretic intersection.
            BNode IDs are not changed."""
-        retval = self.__class__()
+        try:
+            retval = self.__class__()
+        except TypeError:
+            retval = Graph()
         for x in other:
             if x in self:
                 retval.add(x)
@@ -579,7 +585,10 @@ def __mul__(self, other):
     def __sub__(self, other):
         """Set-theoretic difference.
            BNode IDs are not changed."""
-        retval = self.__class__()
+        try:
+            retval = self.__class__()
+        except TypeError:
+            retval = Graph()
         for x in self:
             if x not in other:
                 retval.add(x)

From d605a7086d80686e07252eae333d36e85723b7a3 Mon Sep 17 00:00:00 2001
From: shreyasnagare <shreyasnagare@gmail.com>
Date: Thu, 1 Jul 2021 17:18:30 -0400
Subject: [PATCH 4/4] Use type(self)() instead of self.__class__().

---
 rdflib/graph.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/rdflib/graph.py b/rdflib/graph.py
index 8cbc066d2..b01d33f82 100644
--- a/rdflib/graph.py
+++ b/rdflib/graph.py
@@ -559,7 +559,7 @@ def __add__(self, other):
         """Set-theoretic union
            BNode IDs are not changed."""
         try:
-            retval = self.__class__()
+            retval = type(self)()
         except TypeError:
             retval = Graph()
         for (prefix, uri) in set(list(self.namespaces()) + list(other.namespaces())):
@@ -574,7 +574,7 @@ def __mul__(self, other):
         """Set-theoretic intersection.
            BNode IDs are not changed."""
         try:
-            retval = self.__class__()
+            retval = type(self)()
         except TypeError:
             retval = Graph()
         for x in other:
@@ -586,7 +586,7 @@ def __sub__(self, other):
         """Set-theoretic difference.
            BNode IDs are not changed."""
         try:
-            retval = self.__class__()
+            retval = type(self)()
         except TypeError:
             retval = Graph()
         for x in self: