code: def argval(self):
          
          if gl.has_errors:
              return [None]
  
          if self.asm in ('DEFB', 'DEFS', 'DEFW'):
              return tuple([x.eval() if isinstance(x, Expr) else x for x in self.arg])
  
          self.arg = tuple([x if not isinstance(x, Expr) else x.eval() for x in self.arg])
          if gl.has_errors:
              return [None]
  
          if self.asm.split(' ')[0] in ('JR', 'DJNZ'):  # A relative jump?
              if self.arg[0] < -128 or self.arg[0] > 127:
                  error(self.lineno, 'Relative jump out of range')
                  return [None]
  
          return super(Asm, self).argval()
docs: Solve args values or raise errors if not
          defined yet