code: def validate_all_values_for_key(obj, key, validation_fun):
      
      for vkey, value in obj.items():
          if vkey == key:
              validation_fun(value)
          elif isinstance(value, dict):
              validate_all_values_for_key(value, key, validation_fun)
docs: Validate value for all (nested) occurrence  of `key` in `obj`
         using `validation_fun`.
  
          Args:
              obj (dict): dictionary object.
              key (str): key whose value is to be validated.
              validation_fun (function): function used to validate the value
              of `key`.
  
          Raises:
              ValidationError: `validation_fun` will raise this error on failure