docs: def p_pvar_expr(self, p):
          '''pvar_expr : IDENT LPAREN term_list RPAREN
                       | IDENT'''
          if len(p) == 2:
              p[0] = ('pvar_expr', (p[1], None))
          elif len(p) == 5:
              p[0] = ('pvar_expr', (p[1], p[3]))