2016-09-25 * "Hooli Vest Event"
  Assets:US:Schwab:HOOL               1 HOOL {786.9 USD}
  Income:Salary:Hooli:GSU     CHF @ 0.968892 USD
  Assets:US:Hooli:Unvested:C123456  -1 HOOL.UNVEST
  Expenses:Hooli:Vested              1 HOOL.UNVEST

  Traceback (most recent call last):
    File "/home/erik/.local/lib/python3.7/site-packages/beangulp/__init__.py", line 86, in _extract
      entries = extract.extract_from_file(importer, filename, existing_entries)
    File "/home/erik/.local/lib/python3.7/site-packages/beangulp/extract.py", line 44, in extract_from_file
      entries = importer.deduplicate(entries, existing_entries)
    File "/home/erik/.local/lib/python3.7/site-packages/beangulp/importer.py", line 167, in deduplicate
      return extract.mark_duplicate_entries(entries, existing, window, self.cmp)
    File "/home/erik/.local/lib/python3.7/site-packages/beangulp/extract.py", line 125, in mark_duplicate_entries
      if compare(entry, target):
    File "/home/erik/.local/lib/python3.7/site-packages/beangulp/importer.py", line 145, in cmp
      return compare(a, b)
    File "/home/erik/.local/lib/python3.7/site-packages/beangulp/similar.py", line 101, in __call__
      amounts1 = self.cache[id(entry1)] = amounts_map(entry1)
    File "/home/erik/.local/lib/python3.7/site-packages/beangulp/similar.py", line 151, in amounts_map
      amounts[key] += posting.units.number
  TypeError: unsupported operand type(s) for +=: 'decimal.Decimal' and 'type'