anchor.diff:  ==== `elasticapm.tag()`
   
   Attach tags to the the current transaction and errors.
  +
  +TIP: Before using custom tags, ensure you understand the different types of
  +{apm-overview-ref-v}/metadata.html[metadata] that are available.
  +
   Example:
   
   [source,python]
  
positive.code: following the `update()` semantics of Python dictionaries.
  
  The value is converted to a string.
  
  NOTE: `.`, `*`, and `"` are invalid characters for tag names and will be replaced with `_`.
  
negative.code: 
  Attach custom contextual data to the current transaction and errors.
  Supported frameworks will automatically attach information about the HTTP request and the logged in user.
  You can attach further data using this function.
  
  TIP: Before using custom context, ensure you understand the different types of
  {apm-overview-ref-v}/metadata.html[metadata] that are available.
  
  Example:
  
  [source,python]
  ----
  