fix copy bug

lib/xml_schema_validator/python/xml_schema_validator/__init__.py

@@ -26,7 +26,8 @@ class XmlLogitsProcessor(LogitsProcessor):
         items = dict()
         for token, id in vocab.items():
             items[id] = token
-        self.core = XmlLogitsProcessorCore(items, schema_text)
+        if schema_text:
+            self.core = XmlLogitsProcessorCore(items, schema_text)
         self.prompt_length = None
         self.is_first_call = True
 
@@ -72,4 +73,18 @@ class XmlLogitsProcessor(LogitsProcessor):
                 if token < scores.shape[1]:
                     scores[batch_idx, token] = float('-inf')
 
-        return scores
+        return scores
+
+    def copy(self):
+        """
+        Create a copy of the processor.
+
+        Returns:
+            A new instance of the processor
+        """
+        cloned = XmlLogitsProcessor(self.tokenizer, None)
+        cloned.eos_token_id = self.eos_token_id
+        cloned.core = self.core.copy()
+        cloned.prompt_length = self.prompt_length
+        cloned.is_first_call = self.is_first_call
+        return cloned