code: def get_version(filename, pattern=None):
      
      if pattern is None:
          cre = DEFAULT_VERSION_RE
      else:
          cre = re.compile(pattern)
      with open(filename) as fp:
          for line in fp:
              if line.startswith('__version__'):
                  mo = cre.search(line)
                  assert mo, 'No valid __version__ string found'
                  return mo.group('version')
      raise AssertionError('No __version__ assignment found')
docs: Extract the __version__ from a file without importing it.
  
      While you could get the __version__ by importing the module, the very act
      of importing can cause unintended consequences.  For example, Distribute's
      automatic 2to3 support will break.  Instead, this searches the file for a
      line that starts with __version__, and extract the version number by
      regular expression matching.
  
      By default, two or three dot-separated digits are recognized, but by
      passing a pattern parameter, you can recognize just about anything.  Use
      the `version` group name to specify the match group.
  
      :param filename: The name of the file to search.
      :type filename: string
      :param pattern: Optional alternative regular expression pattern to use.
      :type pattern: string
      :return: The version that was extracted.
      :rtype: string