import unittest
from collections import Counter


def has_palindrome_permutation(xs):
    vs = Counter(xs).values()
    return len([v for v in vs if v % 2 == 1]) in {0, 1}


# Tests
class Test(unittest.TestCase):
    def test_permutation_with_odd_number_of_chars(self):
        result = has_palindrome_permutation('aabcbcd')
        self.assertTrue(result)

    def test_permutation_with_even_number_of_chars(self):
        result = has_palindrome_permutation('aabccbdd')
        self.assertTrue(result)

    def test_no_permutation_with_odd_number_of_chars(self):
        result = has_palindrome_permutation('aabcd')
        self.assertFalse(result)

    def test_no_permutation_with_even_number_of_chars(self):
        result = has_palindrome_permutation('aabbcd')
        self.assertFalse(result)

    def test_empty_string(self):
        result = has_palindrome_permutation('')
        self.assertTrue(result)

    def test_one_character_string(self):
        result = has_palindrome_permutation('a')
        self.assertTrue(result)


unittest.main(verbosity=2)