{{alias}}( value )
    Returns the enumeration constant associated with a supported BLAS matrix
    triangle value.

    Downstream consumers of this function should *not* rely on specific integer
    values (e.g., `UPPER == 0`). Instead, the function should be used in an
    opaque manner.

    Parameters
    ----------
    value: any
        Matrix triangle value.

    Returns
    -------
    out: integer|null
        Enumeration constant.

    Examples
    --------
    > var out = {{alias}}( 'lower' )
    <number>
    > out = {{alias}}( {{alias:@stdlib/blas/base/matrix-triangle-str2enum}}( 'lower' ) )
    <number>

    See Also
    --------