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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 doc_children(self, doctype, limiters=[]):
 """Finds all grand-children of this element's docstrings that match the specified doctype. If 'limiters' is specified, only docstrings with those doctypes are searched. """

        result = []
        for doc in self.docstring:
            if len(limiters) == 0 or doc.doctype in limiters:
                result.extend(doc.children(doctype))

        return result