Add flatten schema function

hed/tools/util/schema_util.py

@@ -0,0 +1,31 @@
+import pandas as pd
+from hed.schema.hed_schema_constants import HedSectionKey
+
+
+def flatten_schema(hed_schema, skip_non_tag=False):
+    """ turns a schema into a 3 column dataframe.
+    Parameters:
+        hed_schema (HedSchema): the schema to flatten
+        skip_non_tag (bool): Skips all sections except tag
+
+    """
+    child, parent, desc = [], [], []
+    for section in hed_schema._sections.values():
+        if skip_non_tag and section.section_key != HedSectionKey.AllTags:
+            continue
+        for entry in section.all_entries:
+            if hasattr(entry, "_parent_tag"):
+                child.append(entry.short_tag_name)
+                if entry._parent_tag:
+                    parent.append(entry._parent_tag.short_tag_name)
+                else:
+                    parent.append("")
+            else:
+                child.append(entry.name)
+                parent.append("")
+
+            desc.append(entry.description)
+
+    df = pd.DataFrame({"Child": child, "Parent": parent, "Description": desc})
+
+    return df