nevermind, that field reference is good

Author: MatheMagicianPi

src/sage/dynamics/arithmetic_dynamics/dynamical_semigroup.py

@@ -457,7 +457,7 @@ def defining_systems(self):
                Defn: Defined on coordinates by sending (x : y) to
                      (x^2 : y^2))
         """
-        return tuple(self.defining_systems())
+        return tuple(self._dynamical_systems)
 
     def _repr_(self):
         r"""