docs: def apply(self, mapping):
          """Apply a mapping of name-value-pairs to a template."""
          mapping = {name: self.str(value, tolerant=self.tolerant)
                     for name, value in mapping.items()
                     if value is not None or self.tolerant}
  
          if self.tolerant:
              return self.template.safe_substitute(mapping)
  
          return self.template.substitute(mapping)