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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 exists(self, table=None):
 """ Return True if the profile or a table exist. If *table* is `None`, this function returns True if the root directory exists and contains a valid relations file. If *table* is given, the function returns True if the table exists as a file (even if empty). Otherwise it returns False. """

        if not os.path.isdir(self.root):
            return False
        if not os.path.isfile(os.path.join(self.root, _relations_filename)):
            return False
        if table is not None:
            try:
                _table_filename(os.path.join(self.root, table))
            except ItsdbError:
                return False
        return True