resnextblock(inplanes, outplanes, cardinality, width, downsample = false)

Create a basic residual block as defined in the paper for ResNeXt (reference).

Arguments:

• inplanes: the number of input feature maps
• outplanes: the number of output feature maps
• cardinality: the number of groups to use for the convolution
• width: the number of feature maps in each group in the bottleneck
• downsample: set to true to downsample the input