Run black, and add black to a "qa" target to make it a standardised process.

src/ifcopenshell-python/ifcopenshell/api/constraint/data.py

@@ -15,10 +15,9 @@ class Data:
         cls.is_loaded = False
         cls.products = {}
         cls.objectives = {}
-        cls.metrics ={}
+        cls.metrics = {}
         cls.references = {}
 
-
     @classmethod
     def load(cls, file, product_id=None):
         cls._file = file