{{alias}}( obj, keys )
    Returns a partial object copy containing only specified keys.

    If a key does not exist as an own property in a source object, the key is
    ignored.

    Parameters
    ----------
    obj: Object
        Source object.

    keys: string|Array<string>
        Keys to copy.

    Returns
    -------
    out: Object
        New object.

    Examples
    --------
    > var obj1 = { 'a': 1, 'b': 2 };
    > var obj2 = {{alias}}( obj1, 'b' )
    { 'b': 2 }

    See Also
    --------