Passing data between two functions. 'bool' object is not callable

I am trying to make desktop-app for my science work.

I have a function that processes the data, and return me 3 list objects. code

  def process(self):    file_location = "'/Users/Graygood/Desktop/Science\ comput/Application/Sheet.xlsx'"    sample = pd.read_excel('Sheet.xlsx', sheetname ='Sheet1', index_col=None, na_values=['NA'])    list_of_index = []    for i in range(len(sample.columns)):        sample2 = sample.iloc[:, lambda sample: [i]]        sample2 = sample2.columns[0]        list_of_index.append(sample2)    list_of_index       ...        ...        ...        ...        ...    ...        ...        ...        ...        ...    ...        ...        ...        ...        ...    return fulllist, fulllist_percent, fulllist_clickdef saveSample(self, process):    fulllist, fulllist_percent, fulllist_click = process(self)    workbook = xlsxwriter.Workbook('lul.xlsx')    worksheet1 = workbook.add_worksheet()    worksheet2 = workbook.add_worksheet()    worksheet3 = workbook.add_worksheet()    row = 0    for col, data in enumerate(fulllist):        worksheet1.write_column(row, col, data)    for col, data in enumerate(fulllist_percent):        worksheet2.write_column(row, col, data)       for col, data in enumerate(fulllist_click):        worksheet3.write_column(row, col, data)          workbook.close()

But when I try to get this lists, i get a "'bool' object is not callable" error. error

I'm pretty new to python, so I might make some stupid mistake, that i do not see