def find_output_at_time(self, ifo, time):
        '''
        Return File that covers the given time.

        Parameters
        -----------
        ifo : string
           Name of the ifo (or ifos) that the File should correspond to
        time : int/float/LIGOGPStime
           Return the Files that covers the supplied time. If no
           File covers the time this will return None.

        Returns
        --------
        list of File classes
           The Files that corresponds to the time.
         '''
        # Get list of Files that overlap time, for given ifo
        outFiles = [i for i in self if ifo in i.ifo_list and time in i.segment_list]
        if len(outFiles) == 0:
            # No OutFile at this time
            return None
        elif len(outFiles) == 1:
            # 1 OutFile at this time (good!)
            return outFiles
        else:
            # Multiple output files. Currently this is valid, but we may want
            # to demand exclusivity later, or in certain cases. Hence the
            # separation.
            return outFiles
Return File that covers the given time.

        Parameters
        -----------
        ifo : string
           Name of the ifo (or ifos) that the File should correspond to
        time : int/float/LIGOGPStime
           Return the Files that covers the supplied time. If no
           File covers the time this will return None.

        Returns
        --------
        list of File classes
           The Files that corresponds to the time.