slan example (#19)

* slan example

* Update docs/index.md

* Update docs/index.md

---------

Co-authored-by: alisterburt <[email protected]>

docs/index.md

@@ -30,6 +30,26 @@ Out[3]:
 
 ```
 
+Annotations made in the [slicer window](https://bio3d.colorado.edu/imod/doc/3dmodHelp/slicer.html) are stored in the IMOD binary file with both centerpoints and angles.
+
+These annotations can be read in by setting `annotation='slan'` when calling `imodmodel.read()`
+
+```python
+import imodmodel
+
+df = imodmodel.read('file_with_slicer_angles.mod', annotation='slan')
+```
+
+```ipython
+In [3]: df.head()
+Out[3]:
+   object_id  slan_id  time      x_rot  y_rot      z_rot    center_x    center_y  center_z label
+0          0        0     1  13.100000    0.0 -30.200001  235.519577  682.744141     302.0
+0          0        1     1 -41.400002    0.0 -47.700001  221.942444  661.193237     327.0
+0          0        2     1 -41.400002    0.0 -41.799999  232.790726  671.332031     327.0
+0          0        3     1 -35.500000    0.0 -36.000000  240.129181  679.927795     324.0
+```
+
 That's it!
 
 ## Installation
@@ -39,4 +59,4 @@ That's it!
 pip install imodmodel
 ```
 
-We recommend installing into a clean virtual environment.
+We recommend installing into a clean virtual environment.