public function set(string $key, $value) : Container
    {
        $this->items[$key] = $value;

        return $this;
    }
public function set(string $key, $value) : Container
    {
        $this->items[$key] = $value;

        return $this;
    }
public function set ( string $ key , $ value ) : Container { $ this -> items [ $ key ] = $ value ; return $ this ; }
Sets a single value.

The value will be returned as is when requested with get().

@param string $key   The key, class or interface name.
@param mixed  $value The value to set.

@return Container
Sets a single value .