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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 set(self, name, value, index=-1):
 """ Assign the ``value`` to the child having the given ``name`` at the ``index`` position :type name: ``str`` :param name: the child name (e.g. PID) :type value: an instance of :class:`Element <hl7apy.core.Element>`, a `str` or an instance of :class:`ElementProxy <hl7apy.core.ElementProxy>` :param value: the child value :type index: ``int`` :param index: the child position (e.g. 1) """


        # just copy the first element of the ElementProxy (e.g. message.pid = message2.pid)
        if isinstance(value, ElementProxy):
            value = value[0].to_er7()

        name = name.upper()
        reference = None if name is None else self.element.find_child_reference(name)
        child_ref, child_name = (None, None) if reference is None else (reference['ref'], reference['name'])

        if isinstance(value, basestring):  # if the value is a basestring, parse it
            child = self.element.parse_child(value, child_name=child_name, reference=child_ref)
        elif isinstance(value, Element):  # it is already an instance of Element
            child = value
        elif isinstance(value, BaseDataType):
            child = self.create_element(name, False, reference)
            child.value = value
        else:
            raise ChildNotValid(value, child_name)

        if child.name != child_name:  # e.g. message.pid = Segment('SPM') is forbidden
            raise ChildNotValid(value, child_name)

        child_to_remove = self.child_at_index(child_name, index)

        if child_to_remove is None:
            self.append(child)
        else:
            self.replace_child(child_to_remove, child)

        # a set has been called, change the temporary parent to be the actual one
        self.element.set_parent_to_traversal()