code: def select(self, *cols):
          
          jdf = self._jdf.select(self._jcols(*cols))
          return DataFrame(jdf, self.sql_ctx)
docs: Projects a set of expressions and returns a new :class:`DataFrame`.
  
          :param cols: list of column names (string) or expressions (:class:`Column`).
              If one of the column names is '*', that column is expanded to include all columns
              in the current DataFrame.
  
          >>> df.select('*').collect()
          [Row(age=2, name=u'Alice'), Row(age=5, name=u'Bob')]
          >>> df.select('name', 'age').collect()
          [Row(name=u'Alice', age=2), Row(name=u'Bob', age=5)]
          >>> df.select(df.name, (df.age + 10).alias('age')).collect()
          [Row(name=u'Alice', age=12), Row(name=u'Bob', age=15)]