code: def _get_function_type(self, function_name):
          
          if (function_name.startswith("Fn::") and
                  function_name[4:] in self.inspect_functions):
              return self.inspect_functions[function_name[4:]]
          return (self.inspect_functions['Ref'] if function_name == "Ref"
                  else None)
docs: Returns the function object that matches the provided name.
          Only Fn:: and Ref functions are supported here so that other
          functions specific to troposphere are skipped.