  from django.utils.datastructures import DictWrapper
  from django.utils.dateparse import (
      parse_date, parse_datetime, parse_duration, parse_time,
  )
  from django.utils.duration import duration_string
  from django.utils.encoding import force_bytes, smart_text
  from django.utils.functional import Promise, cached_property
  from django.utils.ipv6 import clean_ipv6_address
  from django.utils.itercompat import is_iterable
  from django.utils.text import capfirst
 
</s> remove from django.utils.duration import duration_iso_string, duration_string
 </s> add from django.utils.duration import (
    duration_iso_string, duration_microseconds, duration_string,
)
from django.utils.duration import duration_microseconds, duration_string
  from django.utils.datastructures import DictWrapper
  from django.utils.dateparse import (
      parse_date, parse_datetime, parse_duration, parse_time,
  )
from django.utils.duration import duration_microseconds, duration_string
  from django.utils.encoding import force_bytes, smart_text
  from django.utils.functional import Promise, cached_property
  from django.utils.ipv6 import clean_ipv6_address
  from django.utils.itercompat import is_iterable
  from django.utils.text import capfirst
keep keep keep keep replace keep keep keep keep keep
 Fixed #28926 -- Fixed loss of precision of big DurationField values on SQLite and MySQL. 
django/db/models/fields/__init__.py