'Compute virtual evoked using interpolated fields.
.. Warning:: Using virtual evoked to compute inverse can yield
unexpected results. The virtual channels have `\'_virtual\'` appended
at the end of the names to emphasize that the data contained in
them are interpolated.
Parameters
ch_type : str
The destination channel type. It can be \'mag\' or \'grad\'.
mode : str
Either `\'accurate\'` or `\'fast\'`, determines the quality of the
Legendre polynomial expansion used. `\'fast\'` should be sufficient
for most applications.
Returns
evoked : instance of mne.Evoked
The transformed evoked object containing only virtual channels.
Notes
.. versionadded:: 0.9.0'

def as_type(self, ch_type='grad', mode='fast'):

    from .forward import _as_meg_type_evoked
    return _as_meg_type_evoked(self, ch_type=ch_type, mode=mode)
