def invoke_prerequisites(task_args, invocation_chain) # :nodoc:
      @prerequisites.each { |n|
        prereq = application[n, @scope]
        prereq_args = task_args.new_scope(prereq.arg_names)
        prereq.invoke_with_call_chain(prereq_args, invocation_chain)
      }
    end
def invoke_prerequisites(task_args, invocation_chain) # :nodoc:
      @prerequisites.each { |n|
        prereq = application[n, @scope]
        prereq_args = task_args.new_scope(prereq.arg_names)
        prereq.invoke_with_call_chain(prereq_args, invocation_chain)
      }
    end
Invoke all the prerequisites of a task.