class_docstr: - FunctionType.inputs : A list of Type objects defining the types of the input
  - FunctionType.output: A Type object defining the type of the output
  - FunctionType.python_function : The original python function implementing
                                   this type. Two FunctionType objects compare
                                   equal only on inputs and output and not
                                   python_function
code: def __init__(self, inputs, output, python_function=None):
      assert isinstance(inputs, list)
      assert isinstance(output, (FunctionType, Type))
      self.inputs = inputs
      self.output = output
      self.python_function = python_function
  
file_path: coremltools/coremltools/converters/mil/mil/types/type_spec.py
label_desc: Use image node_id 1 to create a new FunctionType object  with example: obj = FunctionType(inputs, output, python_function)