Add some docstrings

src/textual/blank.py

@@ -6,6 +6,15 @@ from rich.style import StyleType
 
 
 class Blank:
+    """
+    Render an empty rectangle.
+
+    Args:
+        style (StyleType): Style to apply to the box.
+        width (int, optional): Width of the box in number of cells. Will expand to fit parent if ``None``.
+        height (int, optional): Height of the box in number of cells. Will expand to fit parent if ``None``.
+    """
+
     def __init__(
         self, style: StyleType, width: int | None = None, height: int | None = None
     ):

src/textual/css/styles.py

@@ -236,6 +236,9 @@ class Styles:
             return None
 
     def reset(self) -> None:
+        """
+        Reset internal style rules to ``None``, reverting to default styles.
+        """
         for rule_name in INTERNAL_RULE_NAMES:
             setattr(self, rule_name, None)