def __init__(<EOL>self,<EOL>api_key,<EOL>base_url='<STR_LIT>'<EOL>):
service_id = api_key[-<NUM_LIT>:-<NUM_LIT>]<EOL>api_key = api_key[-<NUM_LIT>:]<EOL>assert base_url, "<STR_LIT>"<EOL>assert service_id, "<STR_LIT>"<EOL>assert api_key, "<STR_LIT>"<EOL>self.base_url = base_url<EOL>self.service_id = service_id<EOL>self.api_key = api_key<EOL>
Initialise the client
Error if either of base_url or secret missing
:param base_url - base URL of GOV.UK Notify API:
:param secret - application secret - used to sign the request:
:return: