def __init__(self, account_sid, api_key_sid, credential_sid, private_key, pool_connections=True):
self.account_sid = account_sid<EOL>self.credential_sid = credential_sid<EOL>self.api_key_sid = api_key_sid<EOL>self.private_key = private_key<EOL>self.session = Session() if pool_connections else None<EOL>
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.