code: def get_field_by_showname(self, showname):
          
          for field in self._get_all_fields_with_alternates():
              if field.showname_key == showname:
                  # Return it if "XXX: whatever == XXX"
                  return field
docs: Gets a field by its "showname"
          (the name that appears in Wireshark's detailed display i.e. in 'User-Agent: Mozilla...', 'User-Agent' is the
           showname)
  
           Returns None if not found.