code: def to_sparse(self, kind='block', fill_value=None):
          
          # TODO: deprecate
          from pandas.core.sparse.series import SparseSeries
  
          values = SparseArray(self, kind=kind, fill_value=fill_value)
          return SparseSeries(
              values, index=self.index, name=self.name
          ).__finalize__(self)
docs: Convert Series to SparseSeries.
  
          Parameters
          ----------
          kind : {'block', 'integer'}, default 'block'
          fill_value : float, defaults to NaN (missing)
              Value to use for filling NaN values.
  
          Returns
          -------
          SparseSeries
              Sparse representation of the Series.