def add_annotation_to_output_dict(file_id, annotation, output_dict):
    """Updates output_dict with given annotation"""

    if file_id in output_dict.keys(): 
        current_annotations = output_dict[file_id]
        current_annotations.append(annotation)
        output_dict[file_id] = current_annotations
                          
    else:
        output_dict[file_id] = [annotation]

    return output_dict