feat: support Index.to_frame()

bigframes/core/indexes/base.py

@@ -114,6 +114,32 @@ def from_frame(
         index = Index(frame._block)
         index._linked_frame = frame
         return index
+
+    def to_frame(
+        self, index: bool = True, name: blocks.Label | None = None
+    ) -> bigframes.dataframe.DataFrame:
+        import numpy as np
+        provided_name = name if name else self.name
+        provided_index = self.values if index else np.arange(len(self.values))
+        result = bigframes.dataframe.DataFrame({provided_name: self.values}, index= provided_index)
+        if index: # matching pandas behavior
+            result.index.name = self.name
+        return result
+
+    def to_frame(
+        self, index: bool = True, name: blocks.Label | None = None
+    ) -> bigframes.dataframe.DataFrame:
+        import numpy as np
+
+        provided_name = name if name else self.name
+        provided_index = self.values if index else np.arange(len(self.values))
+        result = bigframes.dataframe.DataFrame(
+            {provided_name: self.values}, index=provided_index
+        )
+        if index:  # matching pandas behavior
+            result.index.name = self.name
+
+        return result
 
     @property
     def _session(self):