Is a marriage contract performed by a Shiite sheikh valid, given that both spouses are from the Sunni community, and the text of the contract did not deviate from the Sunnah of Allah and His Messenger?

For a marriage to be valid, it must be contracted by the guardian (wali) or his agent, based on the Prophet's (peace be upon him) saying: "There is no marriage except with a guardian and two just witnesses." The woman's guardian is her father, then his father (paternal grandfather), then her son, then her full brother (from both parents), then her half-brother (from the father only), then their sons, then the paternal uncles, then the ruler. Among the pillars of marriage are the offer (ijab) and acceptance (qabul). The offer comes from the guardian or his agent, and the acceptance comes from the husband or his agent. The offer is the statement made by the guardian or his representative, and the acceptance is the statement made by the husband or his representative. If the contract is concluded in this manner, with the offer from the woman's guardian or his agent, and the acceptance from the husband, in the presence of two Muslim witnesses, or if it is announced and publicized, then the contract is valid, and the status of the marriage officiant (ma'dhun) who registers the contract or prompts the guardian and the husband with the wording of the offer and acceptance has no effect on its validity.