def add_sample_dimension(F, array):
    """
    Add an extra dimension with shape one in the front (axis 0) of an array representing samples.

    :param F: the execution mode of MXNet.
    :type F: mxnet.ndarray or mxnet.symbol
    :param array: the array that the extra dimension is added to.
    :type array: MXNet NDArray or MXNet Symbol
    :returns: the array with the extra dimension.
    :rtypes: the same type as the input array
    """
    return F.expand_dims(array, axis=0)