code: def toDF(self, *cols):
          
          jdf = self._jdf.toDF(self._jseq(cols))
          return DataFrame(jdf, self.sql_ctx)
docs: Returns a new class:`DataFrame` that with new specified column names
  
          :param cols: list of new column names (string)
  
          >>> df.toDF('f1', 'f2').collect()
          [Row(f1=2, f2=u'Alice'), Row(f1=5, f2=u'Bob')]