This operator implements different variants of the alpha miner algorithm The
"classic" variant is defined in http://dx.doi.org/10.1109/TKDE.2004.47 The
"+" variant is defined in http://dx.doi.org/10.1007/978-3-540-30188-2_12 The
"++" variant is defined in http://dx.doi.org/10.1007/s10618-007-0065-y The
"#" variant is defined in http://dx.doi.org/10.1016/j.datak.2010.06.001