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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 json_default(obj):
 """Convert an object to JSON, via the defaults set with register_json_default. :obj: the object to convert """

  for default in _JSON_DEFAULTS:
    if default[0](obj):
      return default[1](obj)
  raise TypeError(repr(obj) + " is not JSON serializable")