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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def convert(self, argument):
 """Returns the int value of argument."""

    if _is_integer_type(argument):
      return argument
    elif isinstance(argument, six.string_types):
      base = 10
      if len(argument) > 2 and argument[0] == '0':
        if argument[1] == 'o':
          base = 8
        elif argument[1] == 'x':
          base = 16
      return int(argument, base)
    else:
      raise TypeError('Expect argument to be a string or int, found {}'.format(
          type(argument)))