docs: def _get_validation(self, method, param):
          """Return the correct validations dictionary for this parameter.
          First checks the method itself and then its class. If no validation is
          defined for this parameter, None is returned.
  
          :param method: A function to get the validation information from.
          :type method: Python function
          :param param: Name of the parameter to get validation information for.
          :type param: str
          """
          if hasattr(method, '_validations') and param in method._validations:
              return method._validations[param]
          elif (hasattr(method.im_class, '_validations') and
                  param in method.im_class._validations):
              return method.im_class._validations[param]
          else:
              return None