parser failed wth "ParameterNotUnderstood: Could not find an action for Header Parameter 'ppt''"

[veluvarti835]

payload ={"alg":"ES256","typ":"passport","ppt":"shaken","x5u":"https://wiresharkserver.mtimslab.atttest.com/vesper/dig-sig.crt"}
payload ={}
header = {"alg":"ES256","typ":"passport","ppt":"shaken","x5u":"https://wiresharkserver.mtimslab.atttest.com/vesper/dig-sig.crt"}
payload = {"attest":"A","dest":{"tn":["+12249587065"]},"iat":1504163217,"orig":{"tn":"+12249587035"},"origid":"6cf14ce7-5c58-403c-8982-07f11b8680d5"}
signature = jws.sign(header, payload, 'secret')
Traceback (most recent call last):
File "", line 1, in
File "/usr/lib/python2.7/site-packages/jws/init.py", line 23, in sign
header.process(data, 'sign')
File "/usr/lib/python2.7/site-packages/jws/header.py", line 67, in process
instance = cls(param, data['header'][param], data)
File "/usr/lib/python2.7/site-packages/jws/header.py", line 10, in init
self.value = self.clean(value)
File "/usr/lib/python2.7/site-packages/jws/header.py", line 30, in clean
raise ParameterNotUnderstood("Could not find an action for Header Parameter '%s'" % self.name)
jws.exceptions.ParameterNotUnderstood: Could not find an action for Header Parameter 'ppt'

[veluvarti835]

After adding ppt header in to known headers got below error , can some one help me to resolve it
KNOWN_HEADERS = {
# REQUIRED, signing algo, see signing_methods
'alg': Algorithm,
# OPTIONAL, type of signed content
'typ': GenericString,
# OPTIONAL, JSON Key URL. See http://self-issued.info/docs/draft-jones-json-web-key.html
'jku': VerifyNotImplemented,
# OPTIONAL, key id, hint for which key to use.
'kid': VerifyNotImplemented,
# OPTIONAL, x.509 URL pointing to certificate or certificate chain
'x5u': VerifyNotImplemented,
# OPTIONAL, x.509 certificate thumbprint
'x5t': VerifyNotImplemented,
# OPTIONAL, type of signed content
'ppt': GenericString,
}

signature = jws.sign(header, payload, 'secret')
Traceback (most recent call last):
File "", line 1, in
File "/usr/lib/python2.7/site-packages/jws/init.py", line 29, in sign
signature = signer(_signing_input(head, payload, is_json), key)
File "/usr/lib/python2.7/site-packages/jws/algos.py", line 127, in sign
return key.sign(msg, hashfunc=self.hasher)
AttributeError: 'str' object has no attribute 'sign'