src/Subjects/FileResolver/SimpleFileResolver.php
protected function preparePattern()
    {
        return sprintf($this->getRegex(), implode($this->getElementSeparator(), $this->resolvePatternValues()), $this->getSuffix());
    }
protected function preparePattern()
    {
        return sprintf($this->getRegex(), implode($this->getElementSeparator(), $this->resolvePatternValues()), $this->getSuffix());
    }
Prepares and returns the pattern for the regex to load the files from the
source directory for the passed subject.

@return string The prepared regex pattern