(types_, typevar_types=None)
return tuple(tvars)
Collect all type variable contained
    in types in order of first appearance (lexicographic order). For example::

        _collect_type_vars((T, List[S, T])) == (T, S)
Collect all type variable contained
    in types in order of first appearance (lexicographic order). For example::
Collect all type variable contained in types in order of first appearance ( lexicographic order ) . For example ::
def _collect_type_vars(types_, typevar_types=None):
    """Collect all type variable contained
    in types in order of first appearance (lexicographic order). For example::

        _collect_type_vars((T, List[S, T])) == (T, S)
    """
    if typevar_types is None:
        typevar_types = TypeVar
    tvars = []
    for t in types_:
        if isinstance(t, typevar_types) and t not in tvars:
            tvars.append(t)
        if isinstance(t, (_GenericAlias, GenericAlias, types.UnionType)):
            tvars.extend([t for t in t.__parameters__ if t not in tvars])
    return tuple(tvars)
def _collect_type_vars ( types_ , typevar_types = None ) : if typevar_types is None : typevar_types = TypeVar tvars = [ ] for t in types_ : if isinstance ( t , typevar_types ) and t not in tvars : tvars . append ( t ) if isinstance ( t , ( _GenericAlias , GenericAlias , types . UnionType ) ) : tvars . extend ( [ t for t in t . __parameters__ if t not in tvars ] ) return tuple ( tvars )