TKinter: How to set the window icon of a child window (Toplevel)

I am trying to add a window icon to the child windows of the main window embedded in TKinter. For portability (aka no missing files) I have my main window icon set in base64 encoded gif as a variable. I have not been able to replicate this for child windows.

from Tkinter import *

ICON = """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"""

class ChildWindow(Toplevel):
    def __init__(self, callingFrame):
        self.parent = callingFrame
        Toplevel.__init__(self)
        self.title("Child")
        self.initUI()

    def initUI(self):

        #this doesn't work in this class, unlike the first class where it does work.
        global ICON
        self.icon = PhotoImage(data=ICON)
        self.call('wm', 'iconphoto', self.parent._w, self.icon)

        btn = Button(self, text="Close", command=self.destroy)
        btn.pack()


class ParentWindow(object):

    def __init__(self, parent):
        self.parent = parent
        self.parent.title("Parent")
        self.frame = Frame(parent)
        self.initUI()

    def initUI(self):
        global ICON
        self.icon = PhotoImage(data=ICON)
        self.parent.call('wm', 'iconphoto', self.parent._w, self.icon)

        btn = Button(self.parent, text="Child", command=self.opennew)
        btn.pack()

    def opennew(self):
        newwin = ChildWindow(self)

def main():
    root = Tk()
    win = ParentWindow(root)
    root.geometry()
    root.mainloop()


if __name__ == '__main__':
    main()