private boolean isLocal(DataType dt) {
		UniversalID sourceId = dt.getSourceArchive().getSourceArchiveID();
		UniversalID dtmId = dt.getDataTypeManager().getUniversalID();
		return sourceId.equals(dtmId);
	}
Returns true if the given data type's source archive is the same as it's current data
type manager.  This is false if copying a new type from the program to an
external archive.

@param dt the type
@return true if the given type already lives in its source archive
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/datamgr/util/DataTypeTreeCopyMoveTask.java