private void addLineIfValid(int line, List<Line> mutate) {
        if (isValidLine(line)) {
            mutate.add(lines.get(line - 1));
        }
    }
This class loads model files into memory, one at a time, and either shows leading lines up to a source location or
shows lines that are relevant to a source location use context from a {@link Model}.

<p>Sort sequences of {@link SourceLocation}s before calling {@link #loadContext(FromSourceLocation)} to avoid
needing to open and parse the same file more than once.

@see SourceContextLoader#createLineBasedLoader
@see SourceContextLoader#createModelAwareLoader
smithy-model/src/main/java/software/amazon/smithy/model/loader/sourcecontext/DefaultSourceLoader.java