Make the docstring a property on the DocstringNode (#35)

Author: stefmolin

src/docstringify/nodes/base.py

@@ -40,13 +40,15 @@ def __init__(
         ) = node
         self.name: str = getattr(node, 'name', self.module_name)
 
-        docstring = ast.get_docstring(node)
-        self.docstring = docstring if docstring is None else docstring.strip()
-
         self.get_source_segment: Callable[[ast.AST], str | None] = partial(
             ast.get_source_segment, source_code
         )
 
+    @property
+    def docstring(self) -> str | None:
+        docstring = ast.get_docstring(self.ast_node)
+        return docstring if docstring is None else docstring.strip()
+
     @property
     def fully_qualified_name(self) -> str:
         return (