Oracle Message PLS-00492 - variable or constant initialization may not refer to functions declared in the same package

ERROR	variable or constant initialization may not refer to functions declared in the same package
CAUSE	If a package spec p declares a function f, that function may not be used in any variable declarations in that same package spec. This is because of a circular instantiation problem: in order to fully instantiate the package spec, the variable must be initialized. To initialize the variable, the function body code in the package body must be executed. That requires that the package body be instantiated. However, the package body cannot be instantiated until the package spec is fully instantiated.
ACTION	Remove the reference to the function from the variable initialization. A technique which often works is to move the variable initialization from the variable declaration (in the package spec) to the package body initialization block.