Added 'edit_terminals' option (Issue #406)

lark/lark.py

@@ -69,6 +69,7 @@ class LarkOptions(Serialize):
         'propagate_positions': False,
         'lexer_callbacks': {},
         'maybe_placeholders': False,
+        'edit_terminals': None,
     }
 
     def __init__(self, options_dict):
@@ -205,6 +206,10 @@ class Lark(Serialize):
         # Compile the EBNF grammar into BNF
         self.terminals, self.rules, self.ignore_tokens = self.grammar.compile(self.options.start)
 
+        if self.options.edit_terminals:
+            for t in self.terminals:
+                self.options.edit_terminals(t)
+
         self._terminals_dict = {t.name:t for t in self.terminals}
 
         # If the user asked to invert the priorities, negate them all here.