ault
    unless `a` has an integer dtype of less precision than the default
    platform integer.  In that case, if `a` is signed then the platform
    integer is used while if `a` is unsigned then an unsigned integer
    of the same precision as the platform integer is used.

    .. versionadded:: 0.18.0

out : np.matrix, optional
    Alternative output matrix in which to place the result. It must
    have the same shape as the expected output, but the type of the
    output values will be cast if necessary.

    .. versionadded:: 0.18.0

Returns
-------
sum_along_axis : np.matrix
    A matrix with the same shape as `self`, with the specified
    axis removed.

See Also
--------
numpy.matrix.sum : NumPy's implementation of 'sum' for matrices

r