code: def save_yaml_model(model, filename, sort=False, **kwargs):
      
      obj = model_to_dict(model, sort=sort)
      obj["version"] = YAML_SPEC
      if isinstance(filename, string_types):
          with io.open(filename, "w") as file_handle:
              yaml.dump(obj, file_handle, **kwargs)
      else:
          yaml.dump(obj, filename, **kwargs)
docs: Write the cobra model to a file in YAML format.
  
      ``kwargs`` are passed on to ``yaml.dump``.
  
      Parameters
      ----------
      model : cobra.Model
          The cobra model to represent.
      filename : str or file-like
          File path or descriptor that the YAML representation should be
          written to.
      sort : bool, optional
          Whether to sort the metabolites, reactions, and genes or maintain the
          order defined in the model.
  
      See Also
      --------
      to_yaml : Return a string representation.
      ruamel.yaml.dump : Base function.