def find_element(strategy, locator, root=None):
Finds an element on the page.

        :param strategy: Location strategy to use (type depends on the driver implementation)
        :param locator: Location of target element.
        :param root: (optional) root node.
        :type strategy: str
        :type locator: str
        :type root: web element object or None.
        :return: web element object
        :rtype: it depends on the driver implementation