def add_header(self, entry):
        """Parses the VCF Header field and returns the number of samples in the VCF file"""
        info = entry.split('\t')
        self.n_individuals = len(info)-9
        for i,v in enumerate(info[9:]):
            self.individuals[v] = i
        return self.n_individuals > 0
Parses the VCF Header field and returns the number of samples in the VCF file