Can a contract for legal services be voided if the contract is not in writing?

^4. Business and Professions Code section 6148 provides, inter alia, that a contract for legal services must be in writing, state any basis of compensation, and specify the nature of the legal services to be provided. Rule 3-300 provides that an attorney cannot enter into a business relationship with a client unless the transaction is fair and disclosed to the client in writing, the client is advised in writing of the right to seek advice from an independent attorney, and the client thereafter consents to the transaction in writing. Probate Code section 16004, subdivision (c) provides that a transaction between a trustee and beneficiary during the existence of a trust is presumed to be a violation of the trustee's fiduciary duties. Agreements that violate the requirements of these statutes may be voided at the client's option. (Bus. & Prof. Code 6148, subd. (c) ["Failure to comply with any provision of this section renders the agreement voidable at the option of the client"]; Fair v. Bakhtiari (2011) 195 Cal.App.4th 1135, 1154 [violations of "Rule 3-300 and section 16004 make the underlying agreements 'voidable not void,' at the election of the client"].)