Create README.md

README.md

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+---
+language:
+- myv
+- ru
+- fi
+- de
+- es
+- en
+- hi
+- zh
+- tr
+- uk
+- fr
+- ar
+tags:
+- erzya
+- mordovian
+- translation
+license: cc-by-sa-4.0
+datasets:
+  - slone/myv_ru_2022
+  - yhavinga/ccmatrix
+---
+
+This a model to translate texts to the Erzya language (`myv`, cyrillic script) from 11 other languages: `ru,fi,de,es,en,hi,zh,tr,uk,fr,ar`.
+
+It is described in the paper "The first neural machine translation system for the Erzya language".
+
+This model is based on [facebook/mbart-large-50](https://huggingface.co/facebook/mbart-large-50) ([license here](https://tfhub.dev/google/LaBSE/2)), but with updated vocabulary and checkpoint:
+- Added an extra language token `myv_XX` and 19K new BPE tokens for the Erzya language;
+- Fine-tuned to translate from Erzya: first to Russian, then to all 11 languages. 
+
+The following code can be used to run translation using the model 
+
+```Python
+from transformers import MBartForConditionalGeneration, MBart50Tokenizer
+
+
+def fix_tokenizer(tokenizer):
+    """ Add a new language token to the tokenizer vocabulary (this should be done each time after its initialization) """
+    old_len = len(tokenizer) - int('myv_XX' in tokenizer.added_tokens_encoder)
+    tokenizer.lang_code_to_id['myv_XX'] = old_len-1
+    tokenizer.id_to_lang_code[old_len-1] = 'myv_XX'
+    tokenizer.fairseq_tokens_to_ids["<mask>"] = len(tokenizer.sp_model) + len(tokenizer.lang_code_to_id) + tokenizer.fairseq_offset
+
+    tokenizer.fairseq_tokens_to_ids.update(tokenizer.lang_code_to_id)
+    tokenizer.fairseq_ids_to_tokens = {v: k for k, v in tokenizer.fairseq_tokens_to_ids.items()}
+    if 'myv_XX' not in tokenizer._additional_special_tokens:
+        tokenizer._additional_special_tokens.append('myv_XX')
+    tokenizer.added_tokens_encoder = {}
+
+
+def translate(text, model, tokenizer, src='ru_RU', trg='myv_XX', max_length='auto', num_beams=3, repetition_penalty=5.0, train_mode=False, n_out=None, **kwargs):
+    tokenizer.src_lang = src
+    encoded = tokenizer(text, return_tensors="pt", truncation=True, max_length=1024)
+    if max_length == 'auto':
+        max_length = int(32 + 1.5 * encoded.input_ids.shape[1])
+    if train_mode:
+        model.train()
+    else:
+        model.eval()
+    generated_tokens = model.generate(
+        **encoded.to(model.device),
+        forced_bos_token_id=tokenizer.lang_code_to_id[trg], 
+        max_length=max_length, 
+        num_beams=num_beams,
+        repetition_penalty=repetition_penalty,
+        num_return_sequences=n_out or 1,
+        **kwargs
+    )
+    out = tokenizer.batch_decode(generated_tokens, skip_special_tokens=True)
+    if isinstance(text, str) and n_out is None:
+        return out[0]
+    return out
+    
+
+mname = 'slone/mbart-large-51-myv-mul-v1'
+model = MBartForConditionalGeneration.from_pretrained(mname)
+tokenizer = MBart50Tokenizer.from_pretrained(mname)
+fix_tokenizer(tokenizer)
+
+
+print(translate('Шумбрат, киска!', model, tokenizer, src='myv_XX', trg='ru_RU'))
+# Привет, собака!   # действительно, "киска" с эрзянского переводится именно так
+print(translate('Шумбрат, киска!', model, tokenizer, src='myv_XX', trg='en_XX'))
+# Hi, dog!
+```