def field(self, name_index):
        """Get a VDField instance representing a field of the vdata.

        Args::

          name_index   name or index number of the field

        Returns::

          VDfield instance representing the field

        C library equivalent : no equivalent
                                                       """

        # Transform a name to an index number
        if isinstance(name_index, str):
            status, index = _C.VSfindex(self._id, name_index)
            _checkErr('field', status, "illegal field name: %s" % name_index)
        else:
            n = _C.VFnfields(self._id)
            _checkErr('field', n, 'cannot execute')
            index = name_index
            if index >= n:
                raise HDF4Error("field: illegal index number")
        return VDField(self, index)
Get a VDField instance representing a field of the vdata.

        Args::

          name_index   name or index number of the field

        Returns::

          VDfield instance representing the field

        C library equivalent : no equivalent