Lesson 3 - data reclassification using Pysal

The below command:
```python
classifier = ps.Natural_Breaks.make(k=n_classes)
```
Fails with the below error:
```python
module 'pysal' has no attribute 'Natural_Breaks'
```
I had to use the following apporach instead (i.e. mapclassify instead of pysal):
```python
import mapclassify as mc
classifier = mc.NaturalBreaks(y=acc[['pt_r_tt']], k=n_classes)
```