Generate `.values()` dict from a table record, removing non-informative values

    Noninformative values include:
      date < 1970
      date > 2100
      False
      None
      0
      0.0
      '0'
      '0.0'
      '0.0000'

def nonnull_fields(obj, pretty=True):
    """Generate `.values()` dict from a table record, removing non-informative values

    Noninformative values include:
      date < 1970
      date > 2100
      False
      None
      0
      0.0
      '0'
      '0.0'
      '0.0000'
    """
    return PrettyDict((k, v) for k, v in [(f.attname, getattr(obj, f.attname, None))
                      for f in obj._meta.fields] if (
                            v and
                            v not in NULL_VALUES and
                            stringify(v).strip().lower()[:MAX_NULL_REPR_LEN] not in NULL_REPR_VALUES and
                            not is_invalid_date(v)))