Brake Fluid Reservoir

I noticed on my 400E at the bottom front right corner of the reservoir (when facing the reservoir) the large black rubber/cloth line is connected to the reservoir with a plastic tie. Is this the proper connector to fasten this line? I’m sorry this is the only way I can identify the line, I know not what it feeds.
Thanks timreid

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timreid
1992 400E
euro lights
500E sway bars
210 16in wheels