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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 _get_extent(self, index):
 """The extent of the full element. E.g., the length of a function call or keyword. """

        extent = 0
        prev_item = get_item(self._items, index - 1)
        seen_dot = prev_item and unicode(prev_item) == '.'
        while index < len(self._items):
            item = get_item(self._items, index)
            index += 1

            if isinstance(item, (ListComprehension, IfExpression)):
                break

            if isinstance(item, Container):
                if prev_item and prev_item.is_name:
                    if seen_dot:
                        extent += 1
                    else:
                        extent += item.size

                    prev_item = item
                    continue
            elif (unicode(item) not in ['.', '=', ':', 'not'] and
                  not item.is_name and not item.is_string):
                break

            if unicode(item) == '.':
                seen_dot = True

            extent += item.size
            prev_item = item

        return extent