code: def pop_source(self):
          "Pop the input source stack."
          self.instream.close()
          (self.infile, self.instream, self.lineno) = self.filestack.popleft()
          if self.debug:
              print('shlex: popping to %s, line %d' \
                    % (self.instream, self.lineno))
          self.state = ' f pop_source(self):
          "Pop the input source stack."
          self.instream.close()
          (self.infile, self.instream, self.lineno) = self.filestack.popleft()
          if self.debug:
              print('shlex: popping to %s, line %d' \
                    % (self.instream, self.lineno))
          self.state = ' '
docs: Pop the input source stack.