class_docstr: A module which performs QKV attention and splits in a different order.
class_docstr_tok: ["A","module","which","performs","QKV","attention","and","splits","in","a","different","order","."]
docstr: Apply QKV attention.
  :param qkv: an [N x (3 * H * C) x T] tensor of Qs, Ks, and Vs.
  :return: an [N x (H * C) x T] tensor after attention.
code: def forward(self, qkv):
      """
      Apply QKV attention.
      :param qkv: an [N x (3 * H * C) x T] tensor of Qs, Ks, and Vs.
      :return: an [N x (H * C) x T] tensor after attention.
      """
      bs, width, length = qkv.shape
      assert width % (3 * self.n_heads) == 0
      ch = width // (3 * self.n_heads)
      q, k, v = qkv.chunk(3, dim=1)
      scale = 1 / math.sqrt(math.sqrt(ch))
      weight = th.einsum(
          "bct,bcs->bts",
          (q * scale).view(bs * self.n_heads, ch, length),
          (k * scale).view(bs * self.n_heads, ch, length),
      )  # More stable with f16 than dividing afterwards
      weight = th.softmax(weight.float(), dim=-1).type(weight.dtype)
      a = th.einsum(
          "bts,bcs->bct",
          weight,
          v.reshape(bs * self.n_heads, ch, length),
      )
      return a.reshape(bs, -1, length)
  
imports: import math
  from abc import abstractmethod
  import numpy
  import torch
  import torch.nn
  import torch.nn.functional
  from ldm.modules.attention import SpatialTransformer
  from ldm.modules.diffusionmodules.util import avg_pool_nd, checkpoint, conv_nd, linear, normalization, timestep_embedding, zero_module
  from ldm.util import exists
label_desc: Use image node_id 2 for calling the QKVAttention obj's underlying member method code with example usage: obj.forward(qkv) and returns: a