@Override
		public DataType promptForDataType(String filterText) {
			DataType dt = dtCache.get(filterText);
			if (dt == null) {
				dt = service.promptForDataType(filterText);
				if (dt != null) {
					dtCache.put(filterText, dt);
				}
			}
			return dt;
		}
Construct caching datatype manager service.
@param service actual datatype manager service which may prompt
user to make a datatype selection.  It is this impementation's 
purpose to cache such a choice for {@link #getDataType(String)} to
avoid repeated selections of the same choice if type is reused
within a function signature.
Ghidra/Features/Base/src/main/java/ghidra/app/util/parser/FunctionSignatureParser.java