Fix Sympy pipeline

Fix #35 (closed)

pystencils/data_types.py

@@ -242,6 +242,9 @@ class TypedSymbol(sp.Symbol):
     def __getnewargs__(self):
         return self.name, self.dtype
 
+    def __getnewargs_ex__(self):
+        return ((self.name, self.dtype), self.assumptions0)
+
     @property
     def canonical(self):
         return self