alias2pkg( alias )
    Returns the package name associated with a provided alias.

    Parameters
    ----------
    alias: any
        Alias (an object path string or reference).

    Returns
    -------
    out: string|undefined
        Package name.

    Examples
    --------
    > var v = alias2pkg( 'base.sin' )
    '@stdlib/math/base/special/sin'


alias2pkg( instance )
    Returns the package name associated with a provided class instance.

    Only direct instances of documented built-in constructors are supported.

    Parameters
    ----------
    instance: any
        Class instance.

    Returns
    -------
    out: string|undefined
        Package name.

    Examples
    --------
    > var v = alias2pkg( new Float64Array( 10 ) )
    '@stdlib/array/float64'

    See Also
    --------
    alias2related, aliases, pkg2alias