What allegation did Danielle Sassoon make regarding Mayor Eric Adams and his attorneys?

Danielle Sassoon alleged a quid pro quo arrangement during an in-person meeting between Adams' attorneys and Department of Justice officials. According to her account, the mayor's representatives offered to help enforce immigration crackdowns in New York City (despite its sanctuary city status) if the DOJ would make the corruption case against Adams disappear. This allegation goes to "the heart of the matter" and was significant enough that Sassoon resigned last week. She perceived this as an inappropriate attempt to trade policy changes for legal leniency, which raised serious ethical concerns about the mayor's administration.