<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_value(self, variable=None):
 """ Gets given environment variable value. :param variable: Variable to retrieve value. :type variable: unicode :return: Variable value. :rtype: unicode :note: If the **variable** argument is not given the first **self.__variables** attribute value will be returned. """


        if variable:
            self.get_values(variable)
            return self.__variables[variable]
        else:
            self.get_values()
            return foundations.common.get_first_item(self.__variables.values())