'Build a ValidationClient which signs requests with private_key and allows Twilio to
validate request has not been tampered with.
:param str account_sid: A Twilio Account Sid starting with \'AC\'
:param str api_key_sid: A Twilio API Key Sid starting with \'SK\'
:param str credential_sid: A Credential Sid starting with \'CR\',
corresponds to public key Twilio will use to verify the JWT.
:param str private_key: The private key used to sign the Client Validation JWT.'

def __init__(self, account_sid, api_key_sid, credential_sid, private_key):

    self.account_sid = account_sid
    self.credential_sid = credential_sid
    self.api_key_sid = api_key_sid
    self.private_key = private_key
