code: def get_declared_enums(metadata, schema, default):
      
      types = set(column.type
                  for table in metadata.tables.values()
                  for column in table.columns
                  if (isinstance(column.type, sqlalchemy.Enum) and
                      schema == (column.type.schema or default)))
      return {t.name: frozenset(t.enums) for t in types}
docs: Return a dict mapping SQLAlchemy enumeration types to the set of their
      declared values.
  
      :param metadata:
          ...
  
      :param str schema:
          Schema name (e.g. "public").
  
      :returns dict:
          {
              "my_enum": frozenset(["a", "b", "c"]),
          }