def list_parents(ChildId=None, NextToken=None, MaxResults=None):
    """
    Lists the root or organizational units (OUs) that serve as the immediate parent of the specified child OU or account. This operation, along with  ListChildren enables you to traverse the tree structure that makes up this root.
    This operation can be called only from the organization's master account.
    See also: AWS API Documentation
    
    
    :example: response = client.list_parents(
        ChildId='string',
        NextToken='string',
        MaxResults=123
    )
    
    
    :type ChildId: string
    :param ChildId: [REQUIRED]
            The unique identifier (ID) of the OU or account whose parent containers you want to list. Do not specify a root.
            The regex pattern for a child ID string requires one of the following:
            Account: a string that consists of exactly 12 digits.
            Organizational unit (OU): a string that begins with 'ou-' followed by from 4 to 32 lower-case letters or digits (the ID of the root that contains the OU) followed by a second '-' dash and from 8 to 32 additional lower-case letters or digits.
            

    :type NextToken: string
    :param NextToken: Use this parameter if you receive a NextToken response in a previous request that indicates that there is more output available. Set it to the value of the previous call's NextToken response to indicate where the output should continue from.

    :type MaxResults: integer
    :param MaxResults: (Optional) Use this to limit the number of results you want included in the response. If you do not include this parameter, it defaults to a value that is specific to the operation. If additional items exist beyond the maximum you specify, the NextToken response element is present and has a value (is not null). Include that value as the NextToken request parameter in the next call to the operation to get the next part of the results. Note that Organizations might return fewer results than the maximum even when there are more results available. You should check NextToken after every operation to ensure that you receive all of the results.

    :rtype: dict
    :return: {
        'Parents': [
            {
                'Id': 'string',
                'Type': 'ROOT'|'ORGANIZATIONAL_UNIT'
            },
        ],
        'NextToken': 'string'
    }
    
    
    :returns: 
    Root: a string that begins with "r-" followed by from 4 to 32 lower-case letters or digits.
    Organizational unit (OU): a string that begins with "ou-" followed by from 4 to 32 lower-case letters or digits (the ID of the root that the OU is in) followed by a second "-" dash and from 8 to 32 additional lower-case letters or digits.
    
    """
    pass
