:param by:
    :param value:
    :param el_class:
    :rtype: tuple[type, str|tuple[str, str]]
    :return:

def define_selector(by, value, el_class):
    """
    :param by:
    :param value:
    :param el_class:
    :rtype: tuple[type, str|tuple[str, str]]
    :return:
    """
    el = el_class
    selector = by
    if isinstance(value, six.string_types):
        selector = (by, value)
    elif value is not None:
        el = value

    if el is None:
        el = elements.PageElement

    return el, selector