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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _GetCallingPrototypeAsString(self, flow_cls):
 """Get a description of the calling prototype for this flow class."""

    output = []
    output.append("flow.StartAFF4Flow(client_id=client_id, ")
    output.append("flow_name=\"%s\", " % flow_cls.__name__)
    prototypes = []
    if flow_cls.args_type:
      for type_descriptor in flow_cls.args_type.type_infos:
        if not type_descriptor.hidden:
          prototypes.append("%s=%s" %
                            (type_descriptor.name, type_descriptor.name))
    output.append(", ".join(prototypes))
    output.append(")")
    return "".join(output)