Officially, police still aren’t talking much about why Assistant Chief Diane Groomes was placed on administrative leave, but the District’s Councilmembers — flooded with calls and emails in support of the popular commander — sure are spilling the beans. At-Large Councilmember Phil Mendelson, who chairs the Council’s Public Safety and Judiciary Committee, told the Post this morning that the test which Groomes is alleged to have helped officers cheat on was an open-book assessment. (Go ahead, get that natural reaction — why would police officers need to cheat on an open-book exam? — out of your system.) But it sounds like the actual problem was that the officers were overdue on the test, not that they were incapable of completing it without Groomes’ assistance. Mendelson told the Post that Groomes said to the cops: “‘Hey, you have to get this done, you are overdue. Here, here’s the answers. Just get this in.” The Fraternal Order of Police is using the incident to question the force’s professionalism — for her part, Groomes, who apologized on Friday, has quite the groundswell of support going for her.