Using findAll two times BeautifulSoup

I'm scraping this webpage with some tables. I want to 'build' two lists and the site have the class 'txt' for two datatypes. I need to extract those datatypes separately, so I'm tryng to "filter" the first type, extract, and then doing the other type.

I made this code:

from bs4 import BeautifulSoupr = requests.get(url, headers=header)soup = BeautifulSoup(r.content, 'html.parser')page = soup.find('div', class_='content')labels = page.findAll('td', class_='label')Output: [<td class="label w15"><span class="help tips" title="Code">?</span><span class="txt">Paper</span></td>,<td class="label destaque w2"><span class="help tips" title="Last value">?</span><span class="txt">Value</span></td>]

I need what is inside those <span class="txt">Paper</span>

When I try this:

myfilter = labels.findAll('span', class_='txt')

I get this error:

AttributeError: ResultSet object has no attribute 'findAll'. You're probably treating a list of elements like a single element. Did you call find_all() when you meant to call find()?

Why? How I can do this?