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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 get_value(self, section, option, default=None):
 """Get the value of an option, if it exists. If it did not exist, then return the default value. It allows user to define dynamic configuration key (see issue#1204) Dynamic vlaue should starts and end with the ` char Example: prefix=`hostname` """

        ret = default
        try:
            ret = self.parser.get(section, option)
        except NoOptionError:
            pass

        # Search a substring `foo` and replace it by the result of its exec
        if ret is not None:
            try:
                match = self.re_pattern.findall(ret)
                for m in match:
                    ret = ret.replace(m, system_exec(m[1:-1]))
            except TypeError:
                pass
        return ret