code: def withColumnRenamed(self, existing, new):
          
          return DataFrame(self._jdf.withColumnRenamed(existing, new), self.sql_ctx)
docs: Returns a new :class:`DataFrame` by renaming an existing column.
          This is a no-op if schema doesn't contain the given column name.
  
          :param existing: string, name of the existing column to rename.
          :param new: string, new name of the column.
  
          >>> df.withColumnRenamed('age', 'age2').collect()
          [Row(age2=2, name=u'Alice'), Row(age2=5, name=u'Bob')]