<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _identify(self, dataframe):
 """Return bool series which is True for indexes that 'pass' the gate"""

        idx = ((dataframe[self.channels[0]] <= self.vert[1]) &
               (dataframe[self.channels[0]] >= self.vert[0]))

        if self.region == 'out':
            idx = ~idx

        return idx