PyQT5と複数の列を使用したテーブルのフィルタリング

PyQt5Pandasデータフレームをテーブルの形式で表示し、MicrosoftExcelフィルターと同様の列フィルターオプションを提供するGUIを作成しようとしています。これまでのところ、私は同様のSO回答を採用することができました。これがGUIの私のテーブルの写真です：

上の図に示すように、列をフィルタリングするには、正規表現フィルターと各列をクリックする2つの方法があります。ただし、対処が必要な問題があります。2番目の列をフィルター処理すると、現在適用されているフィルター（正規表現フィルターまたは列クリック）が消えます。2番目のフィルターをとして必要ですAND。つまり、列1、AND列2を満たすフィルターです。

これが私のコードです：

#!/usr/bin/env python
#-*- coding:utf-8 -*-

from PyQt5 import QtCore, QtGui, QtWidgets

import pandas as pd

class PandasModel(QtCore.QAbstractTableModel):
    def __init__(self, df=pd.DataFrame(), parent=None):
        QtCore.QAbstractTableModel.__init__(self, parent=parent)
        self._df = df.copy()

    def toDataFrame(self):
        return self._df.copy()

    def headerData(self, section, orientation, role=QtCore.Qt.DisplayRole):
        if role != QtCore.Qt.DisplayRole:
            return QtCore.QVariant()

        if orientation == QtCore.Qt.Horizontal:
            try:
                return self._df.columns.tolist()[section]
            except (IndexError, ):
                return QtCore.QVariant()
        elif orientation == QtCore.Qt.Vertical:
            try:
                # return self.df.index.tolist()
                return self._df.index.tolist()[section]
            except (IndexError, ):
                return QtCore.QVariant()

    def data(self, index, role=QtCore.Qt.DisplayRole):
        if role != QtCore.Qt.DisplayRole:
            return QtCore.QVariant()

        if not index.isValid():
            return QtCore.QVariant()

        return QtCore.QVariant(str(self._df.iloc[index.row(), index.column()]))

    def setData(self, index, value, role):
        row = self._df.index[index.row()]
        col = self._df.columns[index.column()]
        if hasattr(value, 'toPyObject'):
            # PyQt4 gets a QVariant
            value = value.toPyObject()
        else:
            # PySide gets an unicode
            dtype = self._df[col].dtype
            if dtype != object:
                value = None if value == '' else dtype.type(value)
        self._df.set_value(row, col, value)
        return True

    def rowCount(self, parent=QtCore.QModelIndex()):
        return len(self._df.index)

    def columnCount(self, parent=QtCore.QModelIndex()):
        return len(self._df.columns)

    def sort(self, column, order):
        colname = self._df.columns.tolist()[column]
        self.layoutAboutToBeChanged.emit()
        self._df.sort_values(colname, ascending= order == QtCore.Qt.AscendingOrder, inplace=True)
        self._df.reset_index(inplace=True, drop=True)
        self.layoutChanged.emit()


class myWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(myWindow, self).__init__(parent)
        self.centralwidget  = QtWidgets.QWidget(self)
        self.lineEdit       = QtWidgets.QLineEdit(self.centralwidget)
        self.view           = QtWidgets.QTableView(self.centralwidget)
        self.comboBox       = QtWidgets.QComboBox(self.centralwidget)
        self.label          = QtWidgets.QLabel(self.centralwidget)

        self.gridLayout = QtWidgets.QGridLayout(self.centralwidget)
        self.gridLayout.addWidget(self.lineEdit, 0, 1, 1, 1)
        self.gridLayout.addWidget(self.view, 1, 0, 1, 3)
        self.gridLayout.addWidget(self.comboBox, 0, 2, 1, 1)
        self.gridLayout.addWidget(self.label, 0, 0, 1, 1)

        self.setCentralWidget(self.centralwidget)
        self.label.setText("Regex Filter")

        self.load_sites()
        self.comboBox.addItems(["{0}".format(col) for col in self.model._df.columns])

        self.lineEdit.textChanged.connect(self.on_lineEdit_textChanged)
        self.comboBox.currentIndexChanged.connect(self.on_comboBox_currentIndexChanged)

        self.horizontalHeader = self.view.horizontalHeader()
        self.horizontalHeader.sectionClicked.connect(self.on_view_horizontalHeader_sectionClicked)


    def load_sites(self):

        df = pd.DataFrame({'site_codes': ['01', '02', '03', '04'],
                           'status': ['open', 'open', 'open', 'closed'],
                           'Location': ['east', 'north', 'south', 'east'],
                           'data_quality': ['poor', 'moderate', 'high', 'high']})

        self.model = PandasModel(df)
        self.proxy = QtCore.QSortFilterProxyModel(self)
        self.proxy.setSourceModel(self.model)
        self.view.setModel(self.proxy)
        self.view.resizeColumnsToContents()

    @QtCore.pyqtSlot(int)
    def on_view_horizontalHeader_sectionClicked(self, logicalIndex):

        self.logicalIndex   = logicalIndex
        self.menuValues     = QtWidgets.QMenu(self)
        self.signalMapper   = QtCore.QSignalMapper(self)
        self.comboBox.blockSignals(True)
        self.comboBox.setCurrentIndex(self.logicalIndex)
        self.comboBox.blockSignals(True)

        valuesUnique = self.model._df.iloc[:, self.logicalIndex].unique()

        actionAll = QtWidgets.QAction("All", self)
        actionAll.triggered.connect(self.on_actionAll_triggered)
        self.menuValues.addAction(actionAll)
        self.menuValues.addSeparator()
        for actionNumber, actionName in enumerate(sorted(list(set(valuesUnique)))):
            action = QtWidgets.QAction(actionName, self)
            self.signalMapper.setMapping(action, actionNumber)
            action.triggered.connect(self.signalMapper.map)
            self.menuValues.addAction(action)
        self.signalMapper.mapped.connect(self.on_signalMapper_mapped)
        headerPos = self.view.mapToGlobal(self.horizontalHeader.pos())
        posY = headerPos.y() + self.horizontalHeader.height()
        posX = headerPos.x() + self.horizontalHeader.sectionPosition(self.logicalIndex)

        self.menuValues.exec_(QtCore.QPoint(posX, posY))

    @QtCore.pyqtSlot()
    def on_actionAll_triggered(self):
        filterColumn = self.logicalIndex
        filterString = QtCore.QRegExp(  "",
                                        QtCore.Qt.CaseInsensitive,
                                        QtCore.QRegExp.RegExp
                                        )

        self.proxy.setFilterRegExp(filterString)
        self.proxy.setFilterKeyColumn(filterColumn)

    @QtCore.pyqtSlot(int)
    def on_signalMapper_mapped(self, i):
        stringAction = self.signalMapper.mapping(i).text()
        filterColumn = self.logicalIndex
        filterString = QtCore.QRegExp(  stringAction,
                                        QtCore.Qt.CaseSensitive,
                                        QtCore.QRegExp.FixedString
                                        )

        self.proxy.setFilterRegExp(filterString)
        self.proxy.setFilterKeyColumn(filterColumn)

    @QtCore.pyqtSlot(str)
    def on_lineEdit_textChanged(self, text):
        search = QtCore.QRegExp(    text,
                                    QtCore.Qt.CaseInsensitive,
                                    QtCore.QRegExp.RegExp
                                    )

        self.proxy.setFilterRegExp(search)

    @QtCore.pyqtSlot(int)
    def on_comboBox_currentIndexChanged(self, index):
        self.proxy.setFilterKeyColumn(index)


if __name__ == "__main__":
    import sys
    app  = QtWidgets.QApplication(sys.argv)
    main = myWindow()
    main.show()
    main.resize(800, 600)
    sys.exit(app.exec_())