function lookup($key)
    {
        if (!isset($this->_styles[$key])) {
            return null;
        }

        return $this->_styles[$key];
    }
function lookup($key)
    {
        if (!isset($this->_styles[$key])) {
            return null;
        }

        return $this->_styles[$key];
    }
function lookup ( $ key ) { if ( ! isset ( $ this -> _styles [ $ key ] ) ) { return null ; } return $ this -> _styles [ $ key ] ; }
lookup a specific Style collection

lookup() returns the Style collection specified by $key, or null if the Style is
not found.

@param string $key the selector of the requested Style
@return Style

@Fixme _styles is a two dimensional array. It should produce wrong results
lookup a specific Style collection