fixed doc strings

Author: smartvinnetou

pandas/core/frame.py

@@ -4477,20 +4477,20 @@ def _maybe_casted_values(index, labels=None):
     # ----------------------------------------------------------------------
     # Reindex-based selection methods
 
-    @Appender(_shared_docs["isna"] % _shared_doc_kwargs)
+    @doc(NDFrame.isna, klass=_shared_doc_kwargs["klass"])
     def isna(self) -> "DataFrame":
         result = self._constructor(self._data.isna(func=isna))
         return result.__finalize__(self)
 
-    @Appender(_shared_docs["isna"] % _shared_doc_kwargs)
+    @doc(NDFrame.isna, klass=_shared_doc_kwargs["klass"])
     def isnull(self) -> "DataFrame":
         return self.isna()
 
-    @Appender(_shared_docs["notna"] % _shared_doc_kwargs)
+    @doc(NDFrame.notna, klass=_shared_doc_kwargs["klass"])
     def notna(self) -> "DataFrame":
         return ~self.isna()
 
-    @Appender(_shared_docs["notna"] % _shared_doc_kwargs)
+    @doc(NDFrame.notna, klass=_shared_doc_kwargs["klass"])
     def notnull(self) -> "DataFrame":
         return ~self.isna()