Format Python code with psf/black push (#75)

There appear to be some python formatting errors in
b201f0a. This pull request
uses the [psf/black](https://github.com/psf/black) formatter to fix
these issues.

dacapo/utils/affinities.py

@@ -9,7 +9,7 @@
 
 
 def seg_to_affgraph(seg: np.ndarray, neighborhood: List[Coordinate]) -> np.ndarray:
-    nhood : np.ndarray = np.array(neighborhood)
+    nhood: np.ndarray = np.array(neighborhood)
 
     # constructs an affinity graph from a segmentation
     # assume affinity graph is represented as: