docs: def emit(self,rlen=150):
        """Emit a read based on a source sequence"""
        source_tx = self._source.emit()
        source_read = self._cutter.cut(source_tx)
        if self._flip and self.options.rand.random() < 0.5: source_read = source_read.rc()
        srname = self.options.rand.uuid4()
        seqfull = FASTQ('@'+self.options.rand.uuid4()+"\tlong\n"+str(source_read.sequence)+"\n+\n"+'I'*source_read.sequence.length+"\n")
        seqperm1 = seqfull.copy()
        seqperm2 = seqfull.copy()
        for e in self.errors:
          seqperm1 = e.permute(seqperm1)
          seqperm2 = e.permute(seqperm2)
        sleft = seqperm1[0:rlen]
        sleft = FASTQ('@'+sleft.name+"\tleft\n"+sleft.sequence+"\n+\n"+sleft.qual+"\n")
        sright = seqperm2.rc()[0:rlen]
        sright = FASTQ('@'+sright.name+"\tright\n"+sright.sequence+"\n+\n"+sright.qual+"\n")
        emission = TranscriptEmission(source_tx,
               Source(source_read,
                      source_read.slice_sequence(0,rlen),
                      source_read.rc().slice_sequence(0,rlen)),
               Read(seqperm1,
                    sleft,
                    sright
                   ))
        return emission