add usage exmaple

README.md

@@ -27,6 +27,21 @@ tags:
 - **Training Duration:** Over 30 hours.
 - **Evaluation Data:** Evaluated on **1,500** (starts from 96425) smart contracts.
 
+## Usage
+
+```python
+from transformers import RobertaTokenizer, RobertaForMaskedLM, pipeline
+
+model = RobertaForMaskedLM.from_pretrained('web3se/SmartBERT-v3')
+tokenizer = RobertaTokenizer.from_pretrained('web3se/SmartBERT-v3')
+
+code_example = "function totalSupply() external view <mask> (uint256);"
+fill_mask = pipeline('fill-mask', model=model, tokenizer=tokenizer)
+
+outputs = fill_mask(code_example)
+print(outputs)
+```
+
 ## Preprocessing
 
 All newline (`\n`) and tab (`\t`) characters in the _function_ code were replaced with a single space to ensure consistency in the input data format.