fix axes method

Author: TrevorBergeron

bigframes/dataframe.py

@@ -346,6 +346,10 @@ def columns(self, labels: pandas.Index):
     def shape(self) -> Tuple[int, int]:
         return self._block.shape
 
+    @property
+    def axes(self) -> list:
+        return [self.index, self.columns]
+
     @property
     def size(self) -> int:
         rows, cols = self.shape

third_party/bigframes_vendored/pandas/core/frame.py

@@ -67,7 +67,7 @@ def axes(self) -> list:
             >>> df.axes[1:]
             [Index(['col1', 'col2'], dtype='object')]
         """
-        return [self.index, self.columns]
+        raise NotImplementedError(constants.ABSTRACT_METHOD_ERROR_MESSAGE)
 
     @property
     def values(self) -> np.ndarray: