Add injection

A new function, `injection` for dependency injection of globals (for classes and functions that weren't designed for dependency injection).

utils.py

@@ -348,6 +348,17 @@ def vector_clip(vector, lowest, highest):
 # ______________________________________________________________________________
 # Misc Functions
 
+class injection():
+    """Dependency injection of temporary values for global functions/classes/etc.
+    E.g., `with injection(DataBase=MockDataBase): ...`"""
+    def __init__(self, **kwds): 
+        self.new = kwds
+    def __enter__(self): 
+        self.old = {v: globals()[v] for v in self.new}
+        globals().update(self.new)
+    def __exit__(self, type, value, traceback): 
+        globals().update(self.old)
+
 
 def memoize(fn, slot=None, maxsize=32):
     """Memoize fn: make it remember the computed value for any argument list.