Inserts a new axis of size 1 into the array shape

def unsqueeze(attrs, inputs, cls):
    """Inserts a new axis of size 1 into the array shape"""
    # MXNet can only add one axis at a time.
    mxnet_op = inputs[0]
    for axis in attrs["axes"]:
        mxnet_op = symbol.expand_dims(mxnet_op, axis=axis)

    return mxnet_op, attrs, inputs