Templating/Helper/Format/FormatHelper.php
public function isSafe($format, $context)
    {
        if (!isset($this->formatterOptions[$format])) {
            return false;
        }

        return $context === $this->formatterOptions[$format]['is_safe'];
    }
public function isSafe($format, $context)
    {
        if (!isset($this->formatterOptions[$format])) {
            return false;
        }

        return $context === $this->formatterOptions[$format]['is_safe'];
    }
@param string $format
@param string $context templating context (e.g. "html")

@return bool