code: def find_referenced_subfiles(self, directory):
          
          if directory is None:
              return []
  
          pattern = r'''[\'\"]?(%s%s[^\s\'\"]+)[\'\"]?''' % (escape(directory), escape(sep))
          return self.find_pattern_references(pattern)
docs: Return list of files below specified `directory` in job inputs. Could
          use more sophisticated logic (match quotes to handle spaces, handle
          subdirectories, etc...).
  
          **Parameters**
  
          directory : str
              Full path to directory to search.