def _evaluate_priority(priority)
      case priority
      when Integer
        _evaluate_priority_int(priority)
      when String, Symbol
        _evaluate_priority_symbol(priority.to_sym)
      when NilClass
        _evaluate_priority_nil
      else
        raise Errors::InvalidPriorityError, priority.inspect
      end
    end
def _evaluate_priority(priority)
      case priority
      when Integer
        _evaluate_priority_int(priority)
      when String, Symbol
        _evaluate_priority_symbol(priority.to_sym)
      when NilClass
        _evaluate_priority_nil
      else
        raise Errors::InvalidPriorityError, priority.inspect
      end
    end
Priority evaluation