What is the relationship between Syriza and Alexis Tsipras in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

Greek Prime Minister Alexis Tsipras had urged his fellow members of parliament to vote 'yes' and survived despite up to 42 rebel votes or abstentions from his Syriza party's MPs, including a 'no' vote from former finance minister Yannis Varoufakis.

Answer: chairperson