code: func (contract *SNativeContractDescription) FunctionByID(id abi.FunctionID) (*SNativeFunctionDescription, errors.CodedError) {
  	f, ok := contract.functionsByID[id]
  	if !ok {
  		return nil,
  			errors.ErrorCodef(errors.ErrorCodeNativeFunction, "unknown SNative function with ID %x", id)
  	}
  	return f, nil
  }
docs: // Get function by calling identifier FunctionSelector