code: def get_pk_constraint(self, connection, table_name, schema=None, **kw):
          
          constraints = self._get_redshift_constraints(connection, table_name,
                                                       schema, **kw)
          pk_constraints = [c for c in constraints if c.contype == 'p']
          if not pk_constraints:
              return {'constrained_columns': [], 'name': ''}
          pk_constraint = pk_constraints[0]
          m = PRIMARY_KEY_RE.match(pk_constraint.condef)
          colstring = m.group('columns')
          constrained_columns = SQL_IDENTIFIER_RE.findall(colstring)
          return {
              'constrained_columns': constrained_columns,
              'name': pk_constraint.conname,
          }
docs: Return information about the primary key constraint on `table_name`.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.interfaces.Dialect.get_pk_constraint`.