docs: add usage guide for check constraints

docs/src/python/check_constraints.py

@@ -1,6 +1,7 @@
 def add_constraint():
     # --8<-- [start:add_constraint]
     from deltalake import DeltaTable
+
     dt = DeltaTable("../rust/tests/data/simple_table")
 
     # Check the schema before hand
@@ -9,12 +10,13 @@ def add_constraint():
     dt.alter.add_constraint({"id_gt_0": "id > 0"})
     # --8<-- [end:add_constraint]
 
+
 def add_data():
     # --8<-- [start:add_data]
     from deltalake import write_deltalake
     import pandas as pd
 
-    df = pd.DataFrame({'id': [-1]})
-    write_deltalake(dt, df, mode='append', engine='rust')
+    df = pd.DataFrame({"id": [-1]})
+    write_deltalake(dt, df, mode="append", engine="rust")
     # _internal.DeltaProtocolError: Invariant violations: ["Check or Invariant (id > 0) violated by value in row: [-1]"]
     # --8<-- [end:add_data]