code: def clear(dest, dest_mapper, synchronize_pairs):
      for l, r in synchronize_pairs:
          if (
              r.primary_key
              and dest_mapper._get_state_attr_by_column(
                  dest, dest.dict, r
              )
              not in orm_util._none_set
          ):
              raise AssertionError(
                  f"Dependency rule on column '{l}' "
                  "tried to blank-out primary key "
                  f"column '{r}' on instance '{orm_util.state_str(dest)}'"
              )
          try:
              dest_mapper._set_state_attr_by_column(
                  dest, dest.dict, r, None
              )
          except exc.UnmappedColumnError as err:
              _raise_col_to_prop(True, None, l, dest_mapper, r, err)
  
file_path: sqlalchemy/lib/sqlalchemy/orm/sync.py
imports: from __future__ import annotations
  from .None import exc
  from .None import util
  from .base import PassiveFlag
label_desc: Use image node_id 3 for calling a global function with example usage: clear(dest, dest_mapper, synchronize_pairs) without return types