Update README.md

README.md

@@ -15,6 +15,11 @@ Clone this repository and install COMBO (we suggest creating a virtualenv/conda
 pip install -U pip setuptools wheel
 pip install --index-url https://pypi.clarin-pl.eu/simple combo==1.0.5
 ```
+For Python 3.9 you may also need to install cython:
+```bash
+pip install -U pip cython
+```
+
 Run the following commands in your Python console to make predictions with a pre-trained model:
 ```python
 from combo.predict import COMBO