What is the open container law in Boston, not regarding motor vehicles?

I thought I remember reading somewhere that Boston doesn't actually have an open container law, but I can't find any information on the laws aside from the ones regarding motor vehicles.

The vast majority of U.S. states and localities prohibit possessing and/or consuming an open container of alcohol in public (i.e. on the street). Only seven states (Georgia, Louisiana, Virginia, Missouri, Montana, Nevada, and Pennsylvania) have no state law against general public possession and/or consumption of an open container by a person of legal drinking age, although nearly all local jurisdictions in those states do prohibit public open containers.

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If its not regarding a motor vehicle what could it be regarding? I don't think its against the law to have an open container if your not in a motor vehicle.

Get caught with one and you will find your sorry a$s in trouble