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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 to_csv(self, file):
 """ Write all the trajectories of a collection to a csv file with the headers 'description', 'time' and 'value'. :param file: a file object to write to :type file: :class:`file` :return: """

        file.write("description,time,value\n")
        for traj in self:
            for t,v in traj:
                file.write("%s,%f,%f\n"% (traj.description.symbol, t, v))