Question on concat pooling syntax

Why is the 2nd argument to f a tuple rather than just an integer (per the docs here)?

def pool(self, x, bs, is_max):
        f = F.adaptive_max_pool1d if is_max else F.adaptive_avg_pool1d
        return f(x.permute(1,2,0), (1,)).view(bs,-1)

Is the adaptive_avg_pool1d function implemented in torch.nn.functional (F) yet? I only see a docstring where the source should be

adaptive_avg_pool1d = _add_docstr(torch.adaptive_avg_pool1d, r"""
adaptive_avg_pool1d(input, output_size) -> Tensor

Applies a 1D adaptive average pooling over an input signal composed of
several input planes.

See :class:~torch.nn.AdaptiveAvgPool1d for details and output shape.

output_size: the target output size (single integer)