private LabelNode toLabelNode(Token label) {
		if (label == null) {
			return null;
		}
		return new LabelNode(label.data, label.startpos, label.endpos);
	}
Parse a stream definition.

@return the AST for the parsed stream
@throws StreamDefinitionException
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/stream/dsl/StreamConfigParser.java