code: @Nullable
      public SoftwareSystem getSoftwareSystemWithId(@Nonnull String id) {
          if (id == null || id.trim().length() == 0) {
              throw new IllegalArgumentException("A software system ID must be specified.");
          }
  
          for (SoftwareSystem softwareSystem : getSoftwareSystems()) {
              if (softwareSystem.getId().equals(id)) {
                  return softwareSystem;
              }
          }
  
          return null;
      }
docs: Gets the software system with the specified ID.
  
  @param id the {@link SoftwareSystem#getId()} of the software system
  @return the SoftwareSystem instance with the specified ID (or null if it doesn't exist).
  @throws IllegalArgumentException if the id is null or empty
  @see SoftwareSystem#getId()