[WIP] Implement subroutine opcodes

Author: Giuseppe Cerami

eth/vm/rstack.py

@@ -30,7 +30,7 @@ class RStack():
     __slots__ = ['values', '_append', '_pop_int', '__len__']
 
     def __init__(self) -> None:
-        values: List[int]
+        values: List[int] = []
         self.values = values
         self._append = values.append
         self._pop_typed = values.pop