Cannot find a child element of a WebElement with By.NAME

I have a parent WebElement in iOS native app, found through find_elementy_by_accessibility_id, and would like to find one of it’s child element.

This following command doesn’t work (gives “An element could not be located on the page using the given search parameters.” error)
parent.find_element(By.NAME, ‘label_headcountnumber’)

But the following command would work.
parent.find_element(By.XPATH, 'XCUIElementTypeStaticText[@name=“label_headcountnumber”])


I’m using Appium 1.7.2. with Python 2.7