Fix: Fix encaspulate Expression._tree when init with random

mapytex/calculus/API/expression.py

@@ -109,12 +109,11 @@ class Expression(object):
         )
         computed = compute_leafs(leafs, generated)
         t = replace_rdleaf(rd_t, computed).map_on_leaf(moify)
-        t = cls._post_precessing(t)
 
         if shuffle:
             raise NotImplemented("Can't suffle expression yet")
 
-        return cls(t)
+        return cls._post_precessing(t)
 
     @classmethod
     def _post_precessing(cls, t):