Extracts a fraction of the file (current chunk of loci) loading
        the genotypes into memoery.

        :param lb: Lower bound of the current chunk
        :param ub: Upper bound of the current chunk
        :return: Dosage dosages for current chunk

def parse_genotypes(self, lb, ub):
        """Extracts a fraction of the file (current chunk of loci) loading
        the genotypes into memoery.

        :param lb: Lower bound of the current chunk
        :param ub: Upper bound of the current chunk
        :return: Dosage dosages for current chunk

        """
        file = self.openfile(self.current_file)
        words = file.readline().strip().split()[lb:ub]
        word_count = len(words)
        idx =0

        if word_count > 0:
            dosages = numpy.empty((self.ind_count, word_count), dtype='|S5')
            while word_count > 1:
                dosages[idx] = numpy.array(words)
                idx += 1
                line = file.readline()
                words = line.strip().split()[lb:ub]
                word_count = len(words)
        else:
            raise EOFError

        return dosages