correct contains method of pda

Author: bygu4

pyformlang/pda/__init__.py

@@ -21,10 +21,12 @@
 """
 
 from .pda import PDA
+from .transition_function import TransitionFunction
 from ..objects.pda_objects import State, Symbol, StackSymbol, Epsilon
 
 
 __all__ = ["PDA",
+           "TransitionFunction",
            "State",
            "Symbol",
            "StackSymbol",

pyformlang/pda/pda.py

@@ -270,7 +270,7 @@ def __contains__(self, transition: InputTransition) -> bool:
         input_symbol = to_symbol(input_symbol)
         stack_from = to_stack_symbol(stack_from)
         s_to = to_state(s_to)
-        stack_to = [to_stack_symbol(x) for x in stack_to]
+        stack_to = tuple(to_stack_symbol(x) for x in stack_to)
         return (s_to, stack_to) in self(s_from, input_symbol, stack_from)
 
     def __iter__(self) -> Iterator[Transition]:

pyformlang/regular_expression/regex.py

@@ -157,19 +157,16 @@ def to_epsilon_nfa(self) -> EpsilonNFA:
         >>> regex.to_epsilon_nfa()
 
         """
-        return self._to_epsilon_nfa_internal(True)
+        return self._to_epsilon_nfa_internal().copy()
 
-    def _to_epsilon_nfa_internal(self, copy: bool) -> EpsilonNFA:
-        """
-        Transforms the regular expression into an epsilon NFA.
-        Copy enfa in case of external usage.
-        """
+    def _to_epsilon_nfa_internal(self) -> EpsilonNFA:
+        """ Transforms the regular expression into an epsilon NFA """
         if self._enfa is None:
             self._enfa = EpsilonNFA()
             s_initial = self._set_and_get_initial_state_in_enfa(self._enfa)
             s_final = self._set_and_get_final_state_in_enfa(self._enfa)
             self._process_to_enfa(self._enfa, s_initial, s_final)
-        return self._enfa.copy() if copy else self._enfa
+        return self._enfa
 
     def _set_and_get_final_state_in_enfa(self, enfa: EpsilonNFA) -> State:
         s_final = self._get_next_state_enfa()
@@ -567,7 +564,7 @@ def accepts(self, word: Iterable[str]) -> bool:
         True
 
         """
-        self._enfa = self._to_epsilon_nfa_internal(False)
+        self._enfa = self._to_epsilon_nfa_internal()
         return self._enfa.accepts(word)
 
     @classmethod