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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def updatetext(self):
 """Recompute textual value based on the text content of the children. Only supported on elements that are a ``TEXTCONTAINER``"""

        if self.TEXTCONTAINER:
            s = ""
            for child in self:
                if isinstance(child, AbstractElement):
                    child.updatetext()
                    s += child.text()
                elif isstring(child):
                    s += child
            self.data = [s]