pub fn col_by_name(&self, col: &str) -> &Column {
        for c in &self.columns {
            if c.name() == col {
                return c;
            }
        }
        panic!("unknown column: {}", col);
    }
/// get column by name
///
/// panics if there is no such column.
get column by name
panics if there is no such column.
get column by name panics if there is no such column .
pub fn col_by_name(&self, col: &str) -> &Column {
        for c in &self.columns {
            if c.name() == col {
                return c;
            }
        }
        panic!("unknown column: {}", col);
    }
pub fn col_by_name ( & self , col : & str ) -> & Column { for c in & self . columns { if c . name ( ) == col { return c ; } } panic ! ( " " col ) ; }
get column by name
panics if there is no such column.
get column by name panics if there is no such column .
&self
col
&str
&self
col
&str