def unsqueeze(data, axis, oldshape):
    """
    Unsqueeze a collapsed array.

    Parameters
    ----------
    data : ndarray
        The data to unsqueeze.
    axis : int
        The axis to unsqueeze.
    oldshape : tuple[int]
        The original shape before the squeeze or reduce operation.

    Returns
    -------
    ndarray
        The unsqueezed array.

    Examples
    --------
    >>> from numpy import mean
    >>> from numpy.random import standard_normal
    >>> x = standard_normal((3,4,5))
    >>> m = mean(x, axis=1)
    >>> m.shape
    (3, 5)
    >>> m = unsqueeze(m, 1, x.shape)
    >>> m.shape
    (3, 1, 5)
    >>>
    """
    newshape = list(oldshape)
    newshape[axis] = 1
    return data.reshape(newshape)
