fix format

README.md

@@ -27,8 +27,10 @@ https://propaganda.qcri.org/annotations/definitions.html
 
 ## How to use
 
+```python
 >>> from .model import BertForTokenAndSequenceJointClassification
 >>> model = BertForTokenAndSequenceJointClassification.from_pretrained(
 >>>     "QCRI/PropagandaTechniquesAnalysis-en-BERT",
 >>>     revision="v0.1.0",
 >>> )
+```