Fix recent error 'Cannot copy out of meta tensor' with flair

transforms_cased.py

@@ -172,7 +172,11 @@ class FilterPOS(BaseTextTransform):
             nltk.download("punkt", quiet=True)
             self.tagger = lambda x: nltk.pos_tag(nltk.word_tokenize(x))
         elif engine == "flair":
-            self.tagger = SequenceTagger.load("flair/pos-english-fast").predict
+            # post-pone loading the flair tagger to avoid a recent error with flair:
+            # NotImplementedError: Cannot copy out of meta tensor; no data! Please use
+            # torch.nn.Module.to_empty() instead of torch.nn.Module.to() when moving module
+            # from meta to a different device.
+            self.tagger = None
 
     def __call__(self, text: str) -> str:
         """
@@ -184,6 +188,14 @@ class FilterPOS(BaseTextTransform):
             text = " ".join([word for word, tag in word_tags if tag not in self.tags])
         elif self.engine == "flair":
             sentence = Sentence(text)
+
+            # post-pone loading the flair tagger to avoid a recent error with flair:
+            # NotImplementedError: Cannot copy out of meta tensor; no data! Please use
+            # torch.nn.Module.to_empty() instead of torch.nn.Module.to() when moving module
+            # from meta to a different device.
+            if self.tagger is None:
+                self.tagger = SequenceTagger.load("flair/pos-english-fast").predict
+
             self.tagger(sentence)
             text = " ".join([token.text for token in sentence.tokens if token.tag in self.tags])