refactor: Swap accessors from inheritance to composition (#2177)

Author: TrevorBergeron

bigframes/core/indexes/base.py

@@ -384,13 +384,13 @@ def to_series(
         name = self.name if name is None else name
         if index is None:
             return bigframes.series.Series(
-                data=self, index=self, name=name, session=self._session
+                data=self, index=self, name=str(name), session=self._session
             )
         else:
             return bigframes.series.Series(
                 data=self,
                 index=Index(index, session=self._session),
-                name=name,
+                name=str(name),
                 session=self._session,
             )
 

bigframes/core/validations.py

@@ -27,7 +27,7 @@
     from bigframes import Session
     from bigframes.core.blocks import Block
     from bigframes.dataframe import DataFrame
-    from bigframes.operations.base import SeriesMethods
+    from bigframes.series import Series
 
 
 class HasSession(Protocol):
@@ -42,7 +42,7 @@ def _block(self) -> Block:
 
 def requires_index(meth):
     @functools.wraps(meth)
-    def guarded_meth(df: Union[DataFrame, SeriesMethods], *args, **kwargs):
+    def guarded_meth(df: Union[DataFrame, Series], *args, **kwargs):
         df._throw_if_null_index(meth.__name__)
         return meth(df, *args, **kwargs)