✨ Convert mods:relatedItem for types original and host

Fixes gh-21.

qurator/mods4pandas/mods4pandas.py

@@ -152,7 +152,15 @@ def mods_to_dict(mods, raise_errors=True):
                 .has_attributes({'authority': 'iso15924', 'type': 'code'}) \
                 .text_set()
         elif tag == '{http://www.loc.gov/mods/v3}relatedItem':
-            pass
+            tag_group = TagGroup(tag, group)
+            for type_, grouped_group in sorted_groupby(tag_group.group, key=lambda g: g.attrib['type']):
+                sub_tag = 'relatedItem-{}'.format(type_)
+                grouped_group = list(grouped_group)
+                if type_ in ["original", "host"]:
+                    value[sub_tag] = TagGroup(sub_tag, grouped_group).is_singleton().descend(raise_errors)
+                else:
+                    # TODO type="series"
+                    pass
         elif tag == '{http://www.loc.gov/mods/v3}name':
             for n, e in enumerate(group):
                 value['name{}'.format(n)] = mods_to_dict(e, raise_errors)

qurator/mods4pandas/tests/test_modstool.py

@@ -1,4 +1,3 @@
-from tkinter import W
 from lxml import etree as ET
 import pytest
 
@@ -126,3 +125,16 @@ def test_originInfo_no_event_type():
 
     assert len(ws) == 1
     assert ws[0].message.args[0] == 'Filtered {http://www.loc.gov/mods/v3}originInfo element (has no eventType)'
+
+def test_relatedItem():
+    d = dict_fromstring("""
+    <mods:mods xmlns:mods="http://www.loc.gov/mods/v3">
+        <mods:relatedItem type="original">
+            <mods:recordInfo>
+                <mods:recordIdentifier source="gbv-ppn">PPN167755803</mods:recordIdentifier>
+            </mods:recordInfo>
+        </mods:relatedItem>
+    </mods:mods>
+    """)
+
+    assert d['relatedItem-original_recordInfo_recordIdentifier'] == 'PPN167755803'