Returns lazy sequence of reference bases. If some bases can't be determined from reads,
they are replaced with 'N'.
Reads must be a range of reads aligned to the same reference sequence, sorted by leftmost
coordinate.
Returned reference bases start from the leftmost position of the first read,
and end at the rightmost position of all the reads.
Returns lazy sequence of reference bases. If some bases can't be determined from reads, they are replaced with 'N'.
Reads must be a range of reads aligned to the same reference sequence, sorted by leftmost coordinate. Returned reference bases start from the leftmost position of the first read, and end at the rightmost position of all the reads.