add empty list test + reformat code

bindings/python/test/test_schema.py

@@ -13,8 +13,8 @@
 # limitations under the License.
 from datetime import datetime
 from unittest import TestCase
-import pytest
 
+import pytest
 from bson import Binary, Code, Decimal128, Int64, ObjectId
 from pyarrow import Table, field, float64, int64, list_, struct, timestamp
 from pyarrow import schema as ArrowSchema
@@ -98,20 +98,19 @@ def test_list_of_list_projection(self):
 
     def test_py_list_projection(self):
         schema = Schema(
-            {
-                "_id": ObjectId, 
-                "list": [(struct([field("a", int64()), field("b", float64())]))]
-            }
+            {"_id": ObjectId, "list": [(struct([field("a", int64()), field("b", float64())]))]}
         )
 
         self.assertEqual(schema._get_projection(), {"_id": True, "list": {"a": True, "b": True}})
 
     def test_py_list_with_multiple_fields_raises(self):
-
-        with pytest.raises(ValueError, match="list field in schema must contain exactly one element, not 2"):
-            _ = Schema(
-                {
-                    "_id": ObjectId, 
-                    "list": [([field("a", int64()), field("b", float64())])]
-                }
-            )
+        with pytest.raises(
+            ValueError, match="list field in schema must contain exactly one element, not 2"
+        ):
+            _ = Schema({"_id": ObjectId, "list": [([field("a", int64()), field("b", float64())])]})
+
+    def test_py_empty_list_raises(self):
+        with pytest.raises(
+            ValueError, match="list field in schema must contain exactly one element, not 0"
+        ):
+            _ = Schema({"_id": ObjectId, "list": []})