Run black over recent Tree tests

Now that we're running black on tests...

tests/tree/test_tree_node_children.py

@@ -1,6 +1,7 @@
 import pytest
 from textual.widgets import Tree, TreeNode
 
+
 def label_of(node: TreeNode[None]):
     """Get the label of a node as a string"""
     return str(node.label)
@@ -8,17 +9,21 @@ def label_of(node: TreeNode[None]):
 
 def test_tree_node_children() -> None:
     """A node's children property should act like an immutable list."""
-    CHILDREN=23
+    CHILDREN = 23
     tree = Tree[None]("Root")
     for child in range(CHILDREN):
         tree.root.add(str(child))
-    assert len(tree.root.children)==CHILDREN
+    assert len(tree.root.children) == CHILDREN
     for child in range(CHILDREN):
         assert label_of(tree.root.children[child]) == str(child)
     assert label_of(tree.root.children[0]) == "0"
-    assert label_of(tree.root.children[-1]) == str(CHILDREN-1)
+    assert label_of(tree.root.children[-1]) == str(CHILDREN - 1)
-    assert [label_of(node) for node in tree.root.children] == [str(n) for n in range(CHILDREN)]
+    assert [label_of(node) for node in tree.root.children] == [
-    assert [label_of(node) for node in tree.root.children[:2]] == [str(n) for n in range(2)]
+        str(n) for n in range(CHILDREN)
+    ]
+    assert [label_of(node) for node in tree.root.children[:2]] == [
+        str(n) for n in range(2)
+    ]
     with pytest.raises(TypeError):
         tree.root.children[0] = tree.root.children[1]
     with pytest.raises(TypeError):

tests/tree/test_tree_node_label.py

@@ -1,6 +1,7 @@
 from textual.widgets import Tree, TreeNode
 from rich.text import Text
 
+
 def test_tree_node_label() -> None:
     """It should be possible to modify a TreeNode's label."""
     node = TreeNode(Tree[None]("Xenomorph Lifecycle"), None, 0, "Facehugger")
@@ -8,6 +9,7 @@ def test_tree_node_label() -> None:
     node.label = "Chestbuster"
     assert node.label == Text("Chestbuster")
 
+
 def test_tree_node_label_via_tree() -> None:
     """It should be possible to modify a TreeNode's label when created via a Tree."""
     tree = Tree[None]("Xenomorph Lifecycle")

tests/tree/test_tree_node_parent.py

@@ -1,5 +1,6 @@
 from textual.widgets import TreeNode, Tree
 
+
 def test_tree_node_parent() -> None:
     """It should be possible to access a TreeNode's parent."""
     tree = Tree[None]("Anakin")