docs: def find_source_files_from_list(self, file_names):
          """
          Finds all source files that actually exists from a list of file names.
  
          :param list[str] file_names: The list of file names.
          """
          for file_name in file_names:
              if os.path.exists(file_name):
                  routine_name = os.path.splitext(os.path.basename(file_name))[0]
                  if routine_name not in self._source_file_names:
                      self._source_file_names[routine_name] = file_name
                  else:
                      self._io.error("Files '{0}' and '{1}' have the same basename.".
                                     format(self._source_file_names[routine_name], file_name))
                      self.error_file_names.add(file_name)
              else:
                  self._io.error("File not exists: '{0}'".format(file_name))
                  self.error_file_names.add(file_name)