docs: def get_tags(self, field):
          """Get the set of tags for a given field.
  
          .. note::
              The named field must be accessible given the current set of values
              defined.
  
          Parameters
          ----------
          field : str
              The field whose tag should be read.
  
          Returns
          -------
          set([tag, ...])
  
          Raises
          ------
          UnavailableFieldError
              If the field does not exist or is not available.
          """
          return self.fields.get_field(field, self.field_values).tags.copy()