def filter(self, chromosome, **kwargs) :
		"""The default filter mixes applied all SNPs and ignores Insertions and Deletions."""
		def appendAllele(alleles, sources, snp) :
			pos = snp.start
			if snp.alt[0] == '-' :
				pass
				# print warn % ('DELETION', snpSet, snp.start, snp.chromosomeNumber)
			elif snp.ref[0] == '-' :
				pass
				# print warn % ('INSERTION', snpSet, snp.start, snp.chromosomeNumber)
			else :
				sources[snpSet] = snp
				alleles.append(snp.alt) #if not an indel append the polymorphism
			
			refAllele = chromosome.refSequence[pos]
			alleles.append(refAllele)
			sources['ref'] = refAllele
			return alleles, sources
				
		warn = 'Warning: the default snp filter ignores indels. IGNORED %s of SNP set: %s at pos: %s of chromosome: %s'
		sources = {}
		alleles = []
		for snpSet, data in kwargs.iteritems() :
			if type(data) is list :
				for snp in data :
					alleles, sources = appendAllele(alleles, sources, snp)
			else :
				allels, sources = appendAllele(alleles, sources, data)

		#appends the refence allele to the lot

		#optional we keep a record of the polymorphisms that were used during the process
		return SequenceSNP(alleles, sources = sources)
The default filter mixes applied all SNPs and ignores Insertions and Deletions.