ENH: more useful table export find func

Summary

1. Add support for passing callable to BaseTableExporter(find_func=callable)
2. Add BaseTableExporter.all_keys.

• Needed for https://git.geomar.de/dm/bis/indiscale/sample-management/-/merge_requests/8

Focus

The magic happens in BaseTableExporter._call_find_function.

Test Environment

Test with geomar setup

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• Reference related issues
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• Appropriate user and developer documentation (or not necessary)
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• Annotations in code (Gitlab comments)
  • Intent of new code
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Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
• Appropriate user and developer documentation (or not necessary)
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src/caosadvancedtools/table_export.py

@@ -27,6 +27,7 @@ them for an export as a table, e.g., for the export to metadata
 repositories.
 
 """
+from inspect import signature
 import json
 import logging
 
@@ -83,7 +84,7 @@ class BaseTableExporter(object):
             ```
             {"entry_to_be_exported: {
                 "optional": True/False
-                "find_func": name of member function
+                "find_func": callable or name of member function
                 "query": query string
                 "selector": selector for the query
                 "error": error explanation
@@ -97,8 +98,8 @@ class BaseTableExporter(object):
             - optional: True or False, if not present, the entry is
               assumed to be mandatory.
             - find_func: name of the member function that returns the
-              value for this entry. Must not exist together with
-              `query`
+              value for this entry or callable object. Must not exist
+              together with `query`
             - query: Query string for finding the value for this
               entry. If this is given, a record must be given to the
               constructor of this class. The query is then executed as
@@ -132,6 +133,7 @@ class BaseTableExporter(object):
         self._check_sanity_of_export_dict()
         self.raise_error_if_missing = raise_error_if_missing
         self.info = {}
+        self.all_keys = [key for key in self.export_dict]
 
     def collect_information(self):
         """Use the items of `export_dict` to collect the information for the
@@ -139,7 +141,8 @@ class BaseTableExporter(object):
 
         """
 
-        for e, d in self.export_dict.items():
+        for e in self.all_keys:
+            d = self.export_dict[e]
             if QUERY in d:
                 # TODO: How do we make this more general? There might
                 # be queries that don't need the record or work with
@@ -163,12 +166,15 @@ class BaseTableExporter(object):
                 else:
                     self._append_missing(e, d)
             elif FIND_FUNCTION in d:
-                find_fun = getattr(self, d[FIND_FUNCTION])
                 try:
-                    self.info[e] = find_fun()
+                    val = self._call_find_function(d[FIND_FUNCTION], e)
+                    if val is not None:
+                        self.info[e] = val
+                    else:
+                        self._append_missing(e, d)
                 except Exception as exc:
                     self._append_missing(e, d)
-                    logger.debug(exc)
+                    logger.error(exc)
             # last resort: check if record has e as property:
             else:
                 try:
@@ -200,6 +206,22 @@ class BaseTableExporter(object):
             else:
                 logger.error(errmssg)
 
+    def _call_find_function(self, find_function, e):
+        account_for_self = 0
+        if callable(find_function):
+            find_fun = find_function
+        else:
+            find_fun = getattr(self, find_function)
+            account_for_self = 1
+
+        sig = signature(find_fun)
+        params = sig.parameters
+        if len(params) > (account_for_self + 1):
+            return find_fun(self.record, e)
+        elif len(params) > account_for_self:
+            return find_fun(self.record)
+        return find_fun()
+
     def prepare_csv_export(self, delimiter=',', print_header=False,
                            skip_empty_optionals=False):
         """Return the values in self.info as a single-line string, separated
@@ -238,7 +260,8 @@ class BaseTableExporter(object):
         if print_header:
             header = ""
 
-        for e, d in self.export_dict.items():
+        for e in self.all_keys:
+            d = self.export_dict[e]
             if e in self.info:
                 body += str(self.info[e]) + delimiter
 
@@ -287,7 +310,9 @@ class BaseTableExporter(object):
             # check find function if present
 
             if FIND_FUNCTION in d:
-                if not hasattr(self, d[FIND_FUNCTION]):
+                if callable(d[FIND_FUNCTION]):
+                    pass
+                elif not hasattr(self, d[FIND_FUNCTION]):
                     raise TableExportError(
                         "Find function " + d[FIND_FUNCTION] +
                         " was specified for entry " + e +