Implement __eq__, __hash__ for CustomCodeNode

pystencils/backends/cbackend.py

@@ -128,6 +128,12 @@ class CustomCodeNode(Node):
     def undefined_symbols(self):
         return self._symbols_read - self._symbols_defined
 
+    def __eq___(self, other):
+        return self._code == other._code
+
+    def __hash__(self):
+        return hash(self._code)
+
 
 class PrintNode(CustomCodeNode):
     # noinspection SpellCheckingInspection