hlaSNPGenoClass: The class of SNP genotypes
In HIBAG: HLA Genotype Imputation with Attribute Bagging

The class of SNP genotypes, and its instance is returned from hlaMakeSNPGeno.

There are five components:

`genotype`	a genotype matrix, “# of SNPs”-by-“# of individuals”; 0 standing for BB (ZERO A allele), 1 for AB (ONE A allele), 2 for AA (TWO A alleles) and others for missing values (missing genotypes are usually set to be NA)
`sample.id`	a vector of sample IDs
`snp.id`	a vector of SNP IDs
`snp.position`	a vector of SNP positions in basepair
`snp.allele`	a vector of characters with a format of “A allele/B allele”
`assembly`	the human genome reference, such like "hg19"