ratio of the input size, this option can be given. This has to
        be a number or tuple in the range (0, 1)
  * **return_indices** -- if "True", will return the indices along
    with the outputs. Useful to pass to "max_unpool3d()".

Shape:
      * Input: (N, C, T_{in}, H_{in}, W_{in}) or (C, T_{in}, H_{in},
        W_{in}).
  * Output: (N, C, T_{out}, H_{out}, W_{out}) or (C, T_{out},
    H_{out}, W_{out}), where (T_{out}, H_{out},
    W_{out})=\text{output\_size} or (T_{out}, H_{out},
    W_{out})=\text{output\_ratio} \times (T_{in}, H_{in}, W_{in})

Examples::
      >>> input = torch.randn(20, 16, 50, 32, 16)
      >>> # pool of cubic window of size=3, and target output size 13x12x11
      >>> F.fractional_max_pool3d(input, 3, output_size=(13, 12, 11))
      >>> # pool of cubic window and target output size being half of input size
      >>> F.fractional_max_pool3d(input, 3, output_ratio=(0.5, 0.5, 0.5))