code: def forward(cls, ctx, X, dim=0, k=None):
      ctx.dim = dim
      Y, _ = _entmax15_forward(X, dim, k)
      ctx.save_for_backward(Y)
      return Y
  
imports: import torch
  import torch.nn
  from torch.autograd import Function
label_desc: Use image node_id 1 for calling the Entmax15Function obj's underlying member method code with example usage: obj.forward(cls, ctx, X, dim, k) and returns: Y