code: def set_key(dotenv_path, key_to_set, value_to_set, quote_mode="always"):
      
      value_to_set = value_to_set.strip("'").strip('"')
      if not os.path.exists(dotenv_path):
          warnings.warn("can't write to %s - it doesn't exist." % dotenv_path)
          return None, key_to_set, value_to_set
  
      if " " in value_to_set:
          quote_mode = "always"
  
      line_template = '{}="{}"\n' if quote_mode == "always" else '{}={}\n'
      line_out = line_template.format(key_to_set, value_to_set)
  
      with rewrite(dotenv_path) as (source, dest):
          replaced = False
          for mapping in parse_stream(source):
              if mapping.key == key_to_set:
                  dest.write(line_out)
                  replaced = True
              else:
                  dest.write(mapping.original)
          if not replaced:
              dest.write(line_out)
  
      return True, key_to_set, value_to_set
docs: Adds or Updates a key/value to the given .env
  
      If the .env path given doesn't exist, fails instead of risking creating
      an orphan .env somewhere in the filesystem