(p)
type_annotation : IDENTIFIER '=' LITERAL
                       | IDENTIFIER
type_annotation : IDENTIFIER '=' LITERAL
                       | IDENTIFIER
type_annotation : IDENTIFIER = LITERAL | IDENTIFIER
def p_type_annotation(p):
    '''type_annotation : IDENTIFIER '=' LITERAL
                       | IDENTIFIER '''
    if len(p) == 4:
        p[0] = p[1], p[3]
    else:
        p[0] = p[1], None
def p_type_annotation ( p ) : if len ( p ) == 4 : p [ 0 ] = p [ 1 ] , p [ 3 ] else : p [ 0 ] = p [ 1 ] , None