The default value to use for substitution, which SHALL be sent if an alternate value is not supplied.
Note this behavior is different than the Schema Object's treatment of default values, because in those cases
parameter values are optional. If the enum is defined, the value SHOULD exist in the enum's values.
Returns the relative, descendent directory path between this module and other.
Throws if no such path exists.
For example, if module mod1 has path /dir1/mod1.pkl, and module mod2 has path /dir1/dir2/dir3/mod2.pkl,
then mod1.relativePathTo(mod2) will return List("dir2", "dir3").
A common use case is to compute the directory path between a template located at the root of a hierarchy
(say rootModule.pkl) and the currently evaluated module (accessible via the module keyword):
An object representing a Server Variable for server URL template substitution.