code: def get_defined_enums(conn, schema):
      
      sql = """
          SELECT
              pg_catalog.format_type(t.oid, NULL),
              ARRAY(SELECT enumlabel
                    FROM pg_catalog.pg_enum
                    WHERE enumtypid = t.oid)
          FROM pg_catalog.pg_type t
          LEFT JOIN pg_catalog.pg_namespace n ON n.oid = t.typnamespace
          WHERE
              t.typtype = 'e'
              AND n.nspname = %s
      """
      return {r[0]: frozenset(r[1]) for r in conn.execute(sql, (schema,))}
docs: Return a dict mapping PostgreSQL enumeration types to the set of their
      defined values.
  
      :param conn:
          SQLAlchemy connection instance.
  
      :param str schema:
          Schema name (e.g. "public").
  
      :returns dict:
          {
              "my_enum": frozenset(["a", "b", "c"]),
          }