@Override
	public SymbolIterator getExternalSymbols(String name) {
		lock.acquire();
		try {
			SymbolIterator symIter = new ExternalSymbolNameRecordIterator(name);
			return symIter;
		}
		catch (IOException e) {
			program.dbError(e);
		}
		finally {
			lock.release();
		}
		return null;
	}
Called by the NamespaceManager when a namespace is removed; remove all symbols that have the
given namespace ID.

@param namespaceID ID of namespace being removed
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/symbol/SymbolManager.java