Repository: titipata/pubmed_parser

Issue:
parse_pubmed_xml does not return "subjects"
**Describe the bug**
Parse PubMed OA XML information appears to have a bug with the "subjects" attribute. 

**To Reproduce**
```
dict_out = pp.parse_pubmed_xml(path)
dict_out["subjects"]
```
Will always be empty. 
https://github.com/titipata/pubmed_parser/blob/1376aa651f05662742e7e225c831c6ffda0dc91b/pubmed_parser/pubmed_oa_parser.py#L148
I believe the following change will fix the issue. 
```
subjects_node = tree.findall(".//article-categories//subj-group/subject")
```

**Expected behavior**
Should return subjects.

Discussion:

Patch:
diff --git a/pubmed_parser/pubmed_oa_parser.py b/pubmed_parser/pubmed_oa_parser.py
index 06b4d25..d05dda9 100644
--- a/pubmed_parser/pubmed_oa_parser.py
+++ b/pubmed_parser/pubmed_oa_parser.py
@@ -145,7 +145,7 @@ def parse_pubmed_xml(path, include_path=False, nxml=False):
     pub_day_node = tree.find(".//pub-date/day")
     pub_day = pub_day_node.text if pub_day_node is not None else "01"
 
-    subjects_node = tree.findall(".//article-categories.//subj-group/subject")
+    subjects_node = tree.findall(".//article-categories//subj-group/subject")
     subjects = list()
     if subjects_node is not None:
         for s in subjects_node:


Test patch:
diff --git a/tests/test_pubmed_oa_parser.py b/tests/test_pubmed_oa_parser.py
index 768c45c..4d44d3f 100644
--- a/tests/test_pubmed_oa_parser.py
+++ b/tests/test_pubmed_oa_parser.py
@@ -14,6 +14,7 @@ def test_parse_pubmed_xml():
     assert len(parsed_xml.get("full_title")) > 0
     assert parsed_xml.get("pmc") == "3460867"
     assert parsed_xml.get("doi") == "10.1371/journal.pone.0046493"
+    assert parsed_xml.get("subjects") == "Research Article; Biology; Biochemistry; Enzymes; Enzyme Metabolism; Lipids; Fatty Acids; Glycerides; Lipid Metabolism; Neutral Lipids; Metabolism; Lipid Metabolism; Proteins; Globular Proteins; Protein Classes; Recombinant Proteins; Biotechnology; Microbiology; Bacterial Pathogens; Bacteriology; Emerging Infectious Diseases; Host-Pathogen Interaction; Microbial Growth and Development; Microbial Metabolism; Microbial Pathogens; Microbial Physiology; Proteomics; Sequence Analysis; Spectrometric Identification of Proteins"
 
 
 def test_parse_pubmed_paragraph():