<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def get_hypervisor():
    '''
    Returns the name of the hypervisor running on this node or ``None``.

    Detected hypervisors:

    - kvm
    - xen
    - bhyve

    CLI Example:

    .. code-block:: bash

        salt '*' virt.get_hypervisor

    .. versionadded:: 2019.2.0
        the function and the ``kvm``, ``xen`` and ``bhyve`` hypervisors support
    '''
    # To add a new 'foo' hypervisor, add the _is_foo_hyper function,
    # add 'foo' to the list below and add it to the docstring with a .. versionadded::
    hypervisors = ['kvm', 'xen', 'bhyve']
    result = [hyper for hyper in hypervisors if getattr(sys.modules[__name__], '_is_{}_hyper'.format(hyper))()]
    return result[0] if result else None