Get/set string file attributes.
When setting file attributes, the file itself is returned so that method calls are chainable.
Name of the attribute.
Value to store.
Get/set user defined string file attributes. When an attribute is not defined on the file, reading it returns the empty value of the type, which is an empty string in case of string.
The maximum length of a string attribute equals that of the file body.
Getting undefined attribute.
Setting attribute on response file.