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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 add_column(self, tablename: str, fieldspec: FIELDSPEC_TYPE) -> int: """Adds a column to an existing table."""

        sql = "ALTER TABLE {} ADD COLUMN {}".format(
            tablename, self.fielddefsql_from_fieldspec(fieldspec))
        log.info(sql)
        return self.db_exec_literal(sql)