# Buggy code
def update_folding(self, ranges):
    """Update folding panel folding ranges."""
    if ranges is None:
        return
    new_folding_ranges = {}
    for starting_line, ending_line in ranges:
        if ending_line > starting_line:
            new_folding_ranges[starting_line + 1] = ending_line + 1

    past_folding_regions = dict(self.folding_regions)
    self.folding_regions = new_folding_ranges
    folding_status = {line: False for line in self.folding_regions}

    if len(folding_status) == len(self.folding_status):
        # No folding lines were introduced before/after
        self.folding_status = dict(
            zip(folding_status.keys(), self.folding_status.values())
        )
    else:
        # Line difference computation is done in order
        # to detect if folding regions were not modified.
        differ = self.editor.differ
        diff, previous_text = self.editor.text_diff
        current_text = self.editor.toPlainText()
        prev_offsets = self.__compute_line_offsets(previous_text)
        current_lines = self.__compute_line_offsets(current_text, True)

        for line in past_folding_regions:
            offset = prev_offsets[line]
            new_offset = differ.diff_xIndex(diff, offset)
            new_line = current_lines[new_offset]
            if new_line in self.folding_regions:
                folding_status[new_line] = self.folding_status[line]
        self.folding_status = folding_status
    # Compute region nesting level
    self.folding_levels = {start_line: 0 for start_line in self.folding_regions}
    self.folding_nesting = {start_line: -1 for start_line in self.folding_regions}
    tree = IntervalTree.from_tuples(self.folding_regions.items())
    for start, end in self.folding_regions.items():
        nested_regions = tree.envelop(start, end)
        for region in nested_regions:
            if region.begin != start:
                self.folding_levels[region.begin] += 1
                self.folding_nesting[region.begin] = start
    self.update()


# Traceback (KeyError)
File "/home/carlos/Projects/spyder/github-repo/spyder/plugins/completion/plugin.py", line 120, in receive_response

Traceback (most recent call last):
File "/home/carlos/Projects/spyder/github-repo/spyder/plugins/completion/plugin.py", line 120, in receive_response
self._maybe_send_locked(req_id)
File "/home/carlos/Projects/spyder/github-repo/spyder/plugins/completion/plugin.py", line 161, in _maybe_send_locked
send()
File "/home/carlos/Projects/spyder/github-repo/spyder/plugins/completion/plugin.py", line 143, in send
self.gather_and_send(request_responses)
File "/home/carlos/Projects/spyder/github-repo/spyder/plugins/completion/plugin.py", line 212, in gather_and_send
response_instance.handle_response(req_type, responses)
File "/home/carlos/Projects/spyder/github-repo/spyder/plugins/editor/widgets/codeeditor.py", line 928, in handle_response
handler(params)
File "/home/carlos/Projects/spyder/github-repo/spyder/plugins/editor/widgets/codeeditor.py", line 1325, in handle_folding_range
folding_panel.update_folding(ranges)
File "/home/carlos/Projects/spyder/github-repo/spyder/plugins/editor/panels/codefolding.py", line 220, in update_folding
folding_status[new_line] = self.folding_status[line]
KeyError: 297

# Fixed code
def update_folding(self, ranges):
    """Update folding panel folding ranges."""
    if ranges is None:
        return
    new_folding_ranges = {}
    for starting_line, ending_line in ranges:
        if ending_line > starting_line:
            new_folding_ranges[starting_line + 1] = ending_line + 1

    past_folding_regions = dict(self.folding_regions.copy())
    self.folding_regions = new_folding_ranges
    folding_status = {line: False for line in self.folding_regions}

    if len(folding_status) == len(self.folding_status):
        # No folding lines were introduced before/after
        self.folding_status = dict(
            zip(folding_status.keys(), self.folding_status.values())
        )
    else:
        # Line difference computation is done in order
        # to detect if folding regions were not modified.
        differ = self.editor.differ
        diff, previous_text = self.editor.text_diff
        current_text = self.editor.toPlainText()
        prev_offsets = self.__compute_line_offsets(previous_text)
        current_lines = self.__compute_line_offsets(current_text, True)

        for line in past_folding_regions:
            offset = prev_offsets.get(line)
            if offset:
                new_offset = differ.diff_xIndex(diff, offset)
                new_line = current_lines.get(new_offset)
                if new_line and new_line in self.folding_regions:
                    try:
                        folding_status[new_line] = self.folding_status[line]
                    except KeyError:
                        pass
        self.folding_status = folding_status
    # Compute region nesting level
    self.folding_levels = {start_line: 0 for start_line in self.folding_regions}
    self.folding_nesting = {start_line: -1 for start_line in self.folding_regions}
    tree = IntervalTree.from_tuples(self.folding_regions.items())
    for start, end in self.folding_regions.items():
        nested_regions = tree.envelop(start, end)
        for region in nested_regions:
            if region.begin != start:
                self.folding_levels[region.begin] += 1
                self.folding_nesting[region.begin] = start
    self.update()