code: public CollisionGroup getGroup(String name)
      {
          Check.notNull(name);
  
          final CollisionGroup group = groups.get(name);
          Check.notNull(group);
  
          return group;
      }
docs: Get a collision formula data from its name.
  
  @param name The formula name (must not be <code>null</code>).
  @return The formula reference.
  @throws LionEngineException If the formula with the specified name is not found.