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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 _replace_placeholder(sql_statement, variable):
 """ Return the string obtained by replacing the specified placeholders by its corresponding value. @param sql_statement: the string expression of a SQL statement to replace placeholders with their corresponding values. @param variable: the variable to use to replace the corresponding placeholder(s) in the SQL statement. * ``name``: name of the variable. * ``type``: an instance of ``PlaceholderType``. * ``value``: the value of this variable to replace the corresponding placeholder(s) of this variable in the SQL statement. @return: a string expression of the SQL statement where the paceholders of the specified variable have been replace by the value of this variable, depending on the type of this varialble. """

        (variable_name, variable_type, variable_value) = variable

        sql_value = RdbmsConnection._expand_placeholder_value(variable_value) if variable_type == PlaceholderType.simple_list \
            else ','.join([ '(%s)' % RdbmsConnection._expand_placeholder_value(v) for v in variable_value ])

        return re.sub(PATTERN_SQL_PLACEHOLDER_EXPRESSIONS[variable_type] % variable_name, sql_value, sql_statement)