Fix: deprecated collections imports

Imports like Sequence, MutableSequence, etc. are deprecated since
python3.3 and are removed from 3.8. This commit fixes these import
problems for users with 3.8+
ref: python/cpython#81505

Author: rseragon

chemdataextractor/config.py

@@ -13,7 +13,7 @@
 from __future__ import unicode_literals
 import io
 import os
-from collections import MutableMapping
+from collections.abc import MutableMapping
 
 import appdirs
 import yaml

chemdataextractor/doc/document.py

@@ -13,7 +13,7 @@
 from __future__ import unicode_literals
 
 from abc import ABCMeta, abstractproperty
-import collections
+from collections.abc import Sequence
 import io
 import json
 import logging
@@ -33,7 +33,7 @@
 
 
 @python_2_unicode_compatible
-class BaseDocument(six.with_metaclass(ABCMeta, collections.Sequence)):
+class BaseDocument(six.with_metaclass(ABCMeta, Sequence)):
     """Abstract base class for a Document."""
 
     def __repr__(self):

chemdataextractor/doc/text.py

@@ -12,7 +12,7 @@
 from __future__ import print_function
 from __future__ import unicode_literals
 from abc import abstractproperty
-import collections
+from collections.abc import Sequence
 import logging
 import re
 
@@ -113,7 +113,7 @@ def _repr_html_(self):
         return self.text
 
 
-class Text(collections.Sequence, BaseText):
+class Text(Sequence, BaseText):
     """A passage of text, comprising one or more sentences."""
 
     sentence_tokenizer = ChemSentenceTokenizer()

chemdataextractor/model.py

@@ -14,7 +14,7 @@
 
 import copy
 from abc import ABCMeta
-from collections import MutableSequence
+from collections.abc import MutableSequence
 import json
 import logging
 

chemdataextractor/parse/elements.py

@@ -11,7 +11,7 @@
 from __future__ import division
 from __future__ import print_function
 from __future__ import unicode_literals
-import collections
+from collections.abc import Sequence
 import copy
 import logging
 import re
@@ -309,7 +309,7 @@ def __init__(self, exprs):
             exprs = list(exprs)
         if isinstance(exprs, six.text_type):
             self.exprs = [Word(exprs)]
-        elif isinstance(exprs, collections.Sequence):
+        elif isinstance(exprs, Sequence):
             if all(isinstance(expr, six.text_type) for expr in exprs):
                 exprs = map(Word, exprs)
             self.exprs = list(exprs)

chemdataextractor/scrape/entity.py

@@ -11,7 +11,7 @@
 from __future__ import division
 from __future__ import print_function
 from __future__ import unicode_literals
-from collections import Sequence
+from collections.abc import Sequence
 import json
 import logging
 

chemdataextractor/scrape/selector.py

@@ -11,7 +11,7 @@
 from __future__ import division
 from __future__ import print_function
 from __future__ import unicode_literals
-from collections import Sequence
+from collections.abc import Sequence
 from copy import deepcopy
 import logging
 import re