'Changed rules so that in hetero ErbB dimers, we only get the species
with the complex bound to one dimer or the other, not both possible
combinations (since we're using a single virtual phosphorylation site
and only allowing one complex bound to a dimer at a time, we're
interested in the dimer as a unit and the specific ErbB unit the complex
is bound to doesn't matter).  Model runs but species haven't been
checked.  Species: 590.  Parameters: 224.'