The legislation instructs the PM, if he cannot achieve an acceptable withdrawal deal, to request a three month extension.
Three months is long enough for a general election but not long enough for a referendum, which is preferred by all the opposition parties except the Labour Party so it looks most likely that we are headed for a general election.
The Liberal Democrats have long campaigned for a People's Vote and that is still the preferred choice of the party. However the policy adopted at the party conference, endorsed by the overwhelming majority of members, is that if a general election comes first, the Liberal Democrats will offer to Revoke Article 50 and Remain, if there is a majority LD government.
In a general election each party puts forward it's platform of policies to tell the electorate what it would do if it became the government.
It is now crystal clear to all voters that the way to stop brexit is to vote Liberal Democrat.