Did Cleopatra die from drinking poison or an asp bite?

Cleopatra died from poison. that much we know. However we don't know exactly what the poison actually was. A German researcher, Dr. Christoph Schaefer, did research on this matter and came to the conclusion that Cleopatra died from a "cocktail" of three poisons, opium, hemlock, and wolfsbane. (maybe yes; maybe no. At any rate all those ingredients were available to her.) Forget about the asp bite. It could not have happened for many reasons.