fixup! ENH: Allow SparseDataFrame/SparseSeries values assignment

Author: kernc

pandas/core/sparse/series.py

@@ -9,7 +9,6 @@
 import warnings
 
 from pandas.core.dtypes.missing import isna, notna
-from pandas.core.dtypes.common import is_sparse
 
 from pandas.compat.numpy import function as nv
 from pandas.core.index import Index, _ensure_index, InvalidIndexError
@@ -528,10 +527,8 @@ def to_dense(self, sparse_only=False):
             index = self.index.take(int_index.indices)
             return Series(self.sp_values, index=index, name=self.name)
         else:
-            values = self.values
-            if is_sparse(values):
-                values = values.to_dense()
-            return Series(values, index=self.index, name=self.name)
+            return Series(self.values.to_dense(), index=self.index,
+                          name=self.name)
 
     @property
     def density(self):