public Collection<AssemblyTerminal> getFirst(AssemblyNonTerminal nt) {
		return Collections.unmodifiableCollection(first.get(nt));
	}
Get the first set for a given non-terminal

<p>
That is the set of all terminals, which through some derivation from the given non-terminal,
can appear first in a sentential form.

@param nt the non-terminal
@return the set
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/app/plugin/assembler/sleigh/parse/AssemblyFirstFollow.java