Folding and Opening a Toy Stroller

“Why are you so sad, Shoshana?!” asked her sister Sari.

“Because on erev Shabbos I folded my toy stroller. And I don’t know if I am allowed to open it on Shabbos,” replied Shoshana with a frown.

“Oh, I see,” said Sari with a sympathetic voice, “Well in two hours, Abba will make Havdalah, and you’ll be able to play with it.”

Their sister Miriam looked at them and said, “Something tells me that a toy like that is okay to open on Shabbos.”

“It could be a problem,” said Sari, “because it’s like you are building it.”

Question: Can Shoshana’s toy stroller be un-folded on Shabbos?