update sorting order of positional metadata

this seems to be a difference in how pd.concat is sorting the columns, and likely coming up because of the `odd_key` used here (an empty `frozendict`). this may be related to this pandas bug fix that went into pandas 1.5.0: pandas-dev/pandas#47331

Author: gregcaporaso

setup.py

@@ -151,7 +151,7 @@
           'matplotlib >= 1.4.3',
           'natsort >= 4.0.3',
           'numpy >= 1.9.2',
-          'pandas >= 1.0.0',
+          'pandas >= 1.5.0',
           'scipy >= 1.9.0',
           'h5py >= 2.9.0',
           'hdmedians >= 0.14.1',

skbio/sequence/tests/test_sequence.py

@@ -167,10 +167,11 @@ def test_concat_strict_simple(self):
         self.assertFalse(result.metadata)
 
     def test_concat_strict_many(self):
+        from collections import OrderedDict
         odd_key = frozenset()
         expected = Sequence("13579",
-                            positional_metadata={'a': list('skbio'),
-                                                 odd_key: [1, 2, 3, 4, 5]})
+                            positional_metadata={odd_key: [1, 2, 3, 4, 5],
+                                                 'a': list('skbio')})
         result = Sequence.concat([
                 Sequence("1", positional_metadata={'a': ['s'], odd_key: [1]}),
                 Sequence("3", positional_metadata={'a': ['k'], odd_key: [2]}),