lookup
Look up the given A_String in the current module's namespace. Answer the atom associated with the string, creating the true name if necessary. A local true name always hides other true names. If isExplicitSubclassAtom is true and we're creating a new atom, add the SpecialAtom.EXPLICIT_SUBCLASSING_KEY property.
Return
An atom.
Parameters
string
An Avail string.
if
An A_Atom lambda to run if the atom had to be created. This should set up basic properties of the new atom, such as heritability and whether it's for explicit object type subclassing.
Throws
If the string could represent several different true names.