_v = \sum_{k = 0}^\infty \frac{(-v)_k (v + 1)_k}{(k!)^2}
                \left(\frac{1 - x}{2}\right)^k

    is the Legendre function of the first kind. Here :math:`(\cdot)_k`
    is the Pochhammer symbol; see `poch`.

    Parameters
    ----------
    m : array_like
        Order (int or float). If passed a float not equal to an
        integer the function returns NaN.
    v : array_like
        Degree (float).
    x : array_like
        Argument (float). Must have ``|x| <= 1``.
    out : ndarray, optional
        Optional output array for the function results

    Returns
    -------
    pmv : scalar or ndarray
        Value of the associated Legendre function.

    See Also
    --------
    lpmn : Compute the associated Legendre function for all orders
           ``0, ..., m`` and degrees ``0, ..., n``.
    clpmn : Compute the associated Legendre function at complex
            arguments.

    Notes
    -----
    Note that this implementation includes the Condon-Shortley phase.

    References
    ----------
    .. [1] Zhang, Jin, "Computation of Special Functions", John Wiley
           and Sons, Inc, 1996.

    