MNVs (multi-nucleotide variants) in dbSNP missing start, end positions

[erikyao]

There are 5 variant types (or vartype's in our code), in dbSNP datasource, a.k.a. SNP classes as listed in Searching dbSNP in Entrez:

"del", "delins", "ins", "mnv", and "snv".

Currently our get_pos_start_end() function failed to handle "mnv" type and therefore start, end positions are missing in those "mnv" documents.