Notwithstanding the President's gift for phraseology … there is no 'favor' involved in Ukraine's investigative cooperation concerning public corruption. You see, there is a Treaty with Ukraine that mutually compels legal assistance in the investigation and prosecution of criminal matters. The Treaty sets forth the procedure for a "Requesting State" and "Requested State" to make and respond to requests for information, documentation, physical evidence, and the deposition and/or physical custody of persons believed to have violated the laws of either one or both treaty signatories. Understand, our Constitution designates the Executive Branch as the branch charged with the faithful execution (enforcement of the law). The President is the head of the Executive Branch and the chief law enforcement officer of the republic. The President's discussion and inquiry concerning former Vice President Biden's publicy and videographically documented admission of misconduct is within the President's Constitutional charge.
Russian conspiracy liar Adam Schiff's hissy fit and your hate Trump tenderized sensibilities notwithstanding … the President had the Constitutional duty to inquire and Ukraine has the obligation to respond pursuant to Treaty 106-16 concerning Mutual Legal Assistance in Criminal Matters.