code: public Object beginContext(Map<URL, ModuleMetaData> mmdi) {
          if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) {
              if (mmdi != null && !mmdi.isEmpty())
                  Tr.debug(tc, "begin context " + mmdi.values().iterator().next().getJ2EEName());
              else
                  Tr.debug(tc, "null or empty object was passed.");
          }
  
          return threadContext.beginContext(mmdi);
      }
docs: Begin the context for the map of ModuleMetaData provided.
  
  @param Map<URL, ModuleMetaData> It Must not be null. Tr.error will be logged if it is null.
  @return Previous Object, which was on the stack. It can be null.