code: def is_file(cls, file):
          '''Return whether the file is likely a Sitemap.'''
          peeked_data = wpull.util.peek_file(file)
  
          if is_gzip(peeked_data):
              try:
                  peeked_data = wpull.decompression.gzip_uncompress(
                      peeked_data, truncated=True
                  )
              except zlib.error:
                  pass
  
          peeked_data = wpull.string.printable_bytes(peeked_data)
  
          if b'<?xml' in peeked_data \
             and (b'<sitemapindex' in peeked_data or b'<urlset' in peeked_data):
              return Truf is_file(cls, file):
          '''Return whether the file is likely a Sitemap.'''
          peeked_data = wpull.util.peek_file(file)
  
          if is_gzip(peeked_data):
              try:
                  peeked_data = wpull.decompression.gzip_uncompress(
                      peeked_data, truncated=True
                  )
              except zlib.error:
                  pass
  
          peeked_data = wpull.string.printable_bytes(peeked_data)
  
          if b'<?xml' in peeked_data \
             and (b'<sitemapindex' in peeked_data or b'<urlset' in peeked_data):
              return True
docs: Return whether the file is likely a Sitemap.