code: def get_boulder_header(key_bytes):
      
      pub_hex, pub_exp = re.search(
          r"modulus:\n\s+00:([a-f0-9\:\s]+?)\npublicExponent: ([0-9]+)",
          key_bytes.decode('utf8'), re.MULTILINE | re.DOTALL).groups()
      pub_exp = "{0:x}".format(int(pub_exp))
      pub_exp = "0{0}".format(pub_exp) if len(pub_exp) % 2 else pub_exp
      header = {
          "alg": "RS256",
          "jwk": {
              "e": _b64(binascii.unhexlify(pub_exp.encode("utf-8"))),
              "kty": "RSA",
              "n": _b64(binascii.unhexlify(re.sub(r"(\s|:)", "", pub_hex).encode("utf-8"))),
          },
      }
  
      return header
docs: Use regular expressions to find crypto values from parsed account key,
      and return a header we can send to our Boulder instance.