code: def dropna(self, axis=0, inplace=False, **kwargs):
          
          # TODO: make more efficient
          # Validate axis
          self._get_axis_number(axis or 0)
          dense_valid = self.to_dense().dropna()
          if inplace:
              raise NotImplementedError("Cannot perform inplace dropna"
                                        " operations on a SparseSeries")
          if isna(self.fill_value):
              return dense_valid
          else:
              dense_valid = dense_valid[dense_valid != self.fill_value]
              return dense_valid.to_sparse(fill_value=self.fill_value)
docs: Analogous to Series.dropna. If fill_value=NaN, returns a dense Series