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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 _RegisterCredentialsMethod(method, position=None):
 """Register a new method for fetching credentials. This new method should be a function with signature: client_info, **kwds -> Credentials or None This method can be used as a decorator, unless position needs to be supplied. Note that method must *always* accept arbitrary keyword arguments. Args: method: New credential-fetching method. position: (default: None) Where in the list of methods to add this; if None, we append. In all but rare cases, this should be either 0 or None. Returns: method, for use as a decorator. """

    if position is None:
        position = len(_CREDENTIALS_METHODS)
    else:
        position = min(position, len(_CREDENTIALS_METHODS))
    _CREDENTIALS_METHODS.insert(position, method)
    return method