The target column uses softmax cross entropy loss.
Args
n_classes
Integer, number of classes, must be >= 2
label_name
String, name of the key in label dict. Can be null if label
is a tensor (single headed models).
weight_column_name
A string defining feature column name representing
weights. It is used to down weight or boost examples during training. It
will be multiplied by the loss of the example.