Formats any additional data that should be appended to the field. Any '%id' entities in the formatted string are replaced with the field's id. Any '%name' entities in the formatted string are replaced with the field's name.
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The formatted addition, the function may return it intact, modified or fully removed if it wished. The only guarantee is that there will be no '%id' or '%name' entities in the result.
Sets one of the firleds attributes. If the attribute does not exist then it is created. The attributes 'id', 'name' and 'value' can not be modified throught this function.