Updated logic for simple variant extraction

Updated the simple variant extraction logic for the case where vcf file isn't tabix indexed to also consider the length of the REF allele.

Author: Rohan-cod

vcf2fhir/json_generator.py

@@ -210,7 +210,7 @@ def _get_fhir_json(
                         not conversion_region or
                         conversion_region[
                             record.CHROM,
-                            record.POS - 1: record.POS
+                            record.POS - 1: (record.POS + len(record.REF) - 1)
                         ].empty is False):
                     _add_record_variants(
                         record, ref_seq, patientID, fhir_helper, ratio_ad_dp)