input: Write a python function to sort a dataset based on the second column.
  assert sort_by_column([[1, 3], [2, 1], [3, 2]]) == [[2, 1], [3, 2], [1, 3]]
  assert sort_by_column([[5, 7], [3, 4], [6, 6], [1, 2]]) == [[1, 2], [3, 4], [6, 6], [5, 7]]
  assert sort_by_column([[2, 3], [1, 1], [4, 4], [3, 2]]) == [[1, 1], [3, 2], [2, 3], [4, 4]]
output: def sort_by_column(dataset):
      return sorted(dataset, key=lambda x: x[1])