code: def related_archives(self):
          
          # Escape the requirement's name for use in a regular expression.
          name_pattern = escape_name(self.name)
          # Escape the requirement's version for in a regular expression.
          version_pattern = re.escape(self.version)
          # Create a regular expression that matches any of the known source
          # distribution archive extensions.
          extension_pattern = '|'.join(re.escape(ext) for ext in ARCHIVE_EXTENSIONS if ext != '.whl')
          # Compose the regular expression pattern to match filenames of source
          # distribution archives in the local source index directory.
          pattern = '^%s-%s(%s)$' % (name_pattern, version_pattern, extension_pattern)
          # Compile the regular expression for case insensitive matching.
          compiled_pattern = re.compile(pattern, re.IGNORECASE)
          # Find the matching source distribution archives.
          return [os.path.join(self.config.source_index, fn)
                  for fn in os.listdir(self.config.source_index)
                  if compiled_pattern.match(fn)]
docs: The pathnames of the source distribution(s) for this requirement (a list of strings).
  
          .. note:: This property is very new in pip-accel and its logic may need
                    some time to mature. For now any misbehavior by this property
                    shouldn't be too much of a problem because the pathnames
                    reported by this property are only used for cache
                    invalidation (see the :attr:`last_modified` and
                    :attr:`checksum` properties).