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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 add_child(self, child):
 """ Add a child """


        rest_name = child.rest_name
        children = self.fetcher_for_rest_name(rest_name)

        if children is None:
            raise InternalConsitencyError('Could not find fetcher with name %s while adding %s in parent %s' % (rest_name, child, self))

        if child not in children:
            child.parent_object = self
            children.append(child)