general: defaultdict fix

(addresses #2030)

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
23: D401 First line should be imperative: 'Trie', not 'Tries'
23: D202 No blank lines allowed *after* function docstring, found 1
23: D400 First line should end with '.', not 't'
23: D205 Blank line missing between one-line summary and description
56: D203 Expected 1 blank line *before* class docstring, found 0
56: D400 First line should end with '.', not ':'
78: D102 Docstring missing
79:27: E714 test for object identity should be 'is not'
81: D401 First line should be imperative: 'A', not 'As'
81: D400 First line should end with '.', not "'"
81: D200 One-line docstring should not occupy 3 lines
113: D102 Docstring missing
121: D400 First line should end with '.', not 's'
125: D102 Docstring missing
135: D102 Docstring missing
139: D102 Docstring missing
142: D102 Docstring missing
145: D102 Docstring missing
148: D102 Docstring missing
151: D102 Docstring missing
154: D102 Docstring missing
157: D102 Docstring missing
160: D102 Docstring missing
163: D102 Docstring missing
166: D202 No blank lines allowed *after* method docstring, found 1
166: D400 First line should end with '.', not 'y'
197:22: E713 test for membership should be 'not in'
205:53: E231 missing whitespace after ','
217: D102 Docstring missing
223: D102 Docstring missing
226: D102 Docstring missing