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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 list_datacenters(kwargs=None, call=None):
    '''
    List all the data centers for this VMware environment

    CLI Example:

    .. code-block:: bash

        salt-cloud -f list_datacenters my-vmware-config
    '''
    if call != 'function':
        raise SaltCloudSystemExit(
            'The list_datacenters function must be called with '
            '-f or --function.'
        )

    return {'Datacenters': salt.utils.vmware.list_datacenters(_get_si())}