# Buggy code
def keyPressEvent(self, event):
    text, key = event.text(), event.key()
    alt = event.modifiers() & Qt.AltModifier
    shift = event.modifiers() & Qt.ShiftModifier
    ctrl = event.modifiers() & Qt.ControlModifier
    modifier = shift or ctrl or alt
    if (
        key in (Qt.Key_Return, Qt.Key_Enter) and self.enter_select
    ) or key == Qt.Key_Tab:
        self.item_selected()
    elif key == Qt.Key_Escape:
        self.hide()
    elif key in (Qt.Key_Return, Qt.Key_Enter, Qt.Key_Left, Qt.Key_Right) or text in (
        ".",
        ":",
    ):
        self.hide()
        self.textedit.keyPressEvent(event)
    elif (
        key
        in (
            Qt.Key_Up,
            Qt.Key_Down,
            Qt.Key_PageUp,
            Qt.Key_PageDown,
            Qt.Key_Home,
            Qt.Key_End,
            Qt.Key_CapsLock,
        )
        and not modifier
    ):
        if key == Qt.Key_Up and self.currentRow() == 0:
            self.setCurrentRow(self.count() - 1)
        elif key == Qt.Key_Down and self.currentRow() == self.count() - 1:
            self.setCurrentRow(0)
        else:
            QListWidget.keyPressEvent(self, event)
    elif len(text) or key == Qt.Key_Backspace:
        # If the cursor goes behind the current position,
        # the autocomplete is no longer relevant
        if self.textedit.textCursor().position() < self.position or (
            key == Qt.Key_Backspace
            and (self.textedit.textCursor().position() <= self.position)
        ):
            self.hide()
            self.textedit.keyPressEvent(event)
        else:
            self.textedit.keyPressEvent(event)
            self.update_current()
    elif modifier:
        self.textedit.keyPressEvent(event)
    else:
        self.hide()
        QListWidget.keyPressEvent(self, event)


# Traceback (AttributeError)
File "C:\Users\C. A. M. Gerlach\Documents\dev\SpyderDev\spyder\spyder\plugins\editor\lsp\client.py", line 230, in on_msg_received
handler(resp['result'], req_id)
File "C:\Users\C. A. M. Gerlach\Documents\dev\SpyderDev\spyder\spyder\plugins\editor\lsp\providers\document.py", line 117, in process_document_completion
LSPRequestTypes.DOCUMENT_COMPLETION, {'params': response})
File "C:\Users\C. A. M. Gerlach\Documents\dev\SpyderDev\spyder\spyder\plugins\editor\widgets\codeeditor.py", line 690, in handle_response
handler(params)
File "C:\Users\C. A. M. Gerlach\Documents\dev\SpyderDev\spyder\spyder\plugins\editor\widgets\codeeditor.py", line 790, in process_completion
self.completion_widget.show_list(completion_list, position)
File "C:\Users\C. A. M. Gerlach\Documents\dev\SpyderDev\spyder\spyder\plugins\editor\widgets\base.py", line 159, in show_list
self.update_current()
File "C:\Users\C. A. M. Gerlach\Documents\dev\SpyderDev\spyder\spyder\plugins\editor\widgets\base.py", line 222, in update_current
completion_label = completion.lower()
AttributeError: 'dict' object has no attribute 'lower'

# Fixed code
def keyPressEvent(self, event):
    text, key = event.text(), event.key()
    alt = event.modifiers() & Qt.AltModifier
    shift = event.modifiers() & Qt.ShiftModifier
    ctrl = event.modifiers() & Qt.ControlModifier
    modifier = shift or ctrl or alt
    if key in (Qt.Key_Return, Qt.Key_Enter) or key == Qt.Key_Tab:
        self.item_selected()
    elif key == Qt.Key_Escape:
        self.hide()
    elif key in (Qt.Key_Return, Qt.Key_Enter, Qt.Key_Left, Qt.Key_Right) or text in (
        ".",
        ":",
    ):
        self.hide()
        self.textedit.keyPressEvent(event)
    elif (
        key
        in (
            Qt.Key_Up,
            Qt.Key_Down,
            Qt.Key_PageUp,
            Qt.Key_PageDown,
            Qt.Key_Home,
            Qt.Key_End,
            Qt.Key_CapsLock,
        )
        and not modifier
    ):
        if key == Qt.Key_Up and self.currentRow() == 0:
            self.setCurrentRow(self.count() - 1)
        elif key == Qt.Key_Down and self.currentRow() == self.count() - 1:
            self.setCurrentRow(0)
        else:
            QListWidget.keyPressEvent(self, event)
    elif len(text) or key == Qt.Key_Backspace:
        # If the cursor goes behind the current position,
        # the autocomplete is no longer relevant
        if self.textedit.textCursor().position() < self.position or (
            key == Qt.Key_Backspace
            and (self.textedit.textCursor().position() <= self.position)
        ):
            self.hide()
            self.textedit.keyPressEvent(event)
        else:
            self.textedit.keyPressEvent(event)
            self.update_current()
    elif modifier:
        self.textedit.keyPressEvent(event)
    else:
        self.hide()
        QListWidget.keyPressEvent(self, event)