def schedule_lock(*types)
      types.each do |type|
        validations_for(:"base_#{type}") << Validation.new(type)
      end
    end
def schedule_lock(*types)
      types.each do |type|
        validations_for(:"base_#{type}") << Validation.new(type)
      end
    end
Lock the given time units to the units from schedule's +start_time+
 These locks are all clobberable by other rules of the same #type
 using +clobber_base_validation+