Spectra: remove unused function 'get_relative_to_value'

src/est/core/types/spectra.py

@@ -132,13 +132,6 @@ class Spectra:
             else:
                 return object[name]
 
-        def get_relative_to_value(relative):
-            paths_ = relative.split(".")
-            value = getattr(self.data.flat[0], paths_[0])
-            for path_ in paths_[1:]:
-                value = getattr(value, path_)
-            return value
-
         if len(self.data.flat) == 0:
             return None