Mamata Banerjee, West Bengal's mercurial chief minister, will accompany Prime Minister Narendra Modi to Dhaka this weekend. Three years ago, she had abruptly walked out of a similar visit accompanying then PM Manmohan Singh. Land boundary agreements, water sharing pacts and national security along the border - all need the critical cooperation of Kolkata's government. Will Ms Banerjee keep her word this time? And if so what's changed between India-Bangla ties to make her agree?