@staticmethod
def _build_variant_label(build, chromosome, position, reference_allele,
    variant_allele, gene_symbols=None):
    """
        Function to build HGVS variant labels
        :param build: {str} build id
        :param chromosome: {str} chromosome
        :param position: {str} variation position as string or int
        :param reference_allele: {str} single letter ref bp
        :param variant_allele: {str} single letter bp change
        :param gene_symbol: {str} gene symbol (hgvs)
        :return: {str} variant label
        """
    variant_label = ''
    prefix = ''
    if gene_symbols and len(gene_symbols) == 1 and gene_symbols[0]:
        prefix = '{0}{1}({2})'.format(build, chromosome, gene_symbols[0])
    else:
        prefix = '{0}{1}'.format(build, chromosome)
    if reference_allele == '-':
        variant_label = '{0}:g.{1}ins{2}'.format(prefix, position,
            variant_allele)
    elif variant_allele == '-':
        variant_label = '{0}:g.{1}del{2}'.format(prefix, position,
            reference_allele)
    else:
        variant_label = '{0}:g.{1}{2}>{3}'.format(prefix, position,
            reference_allele, variant_allele)
    return variant_label
