How to use the sardana.macroserver.scan.scandata.ColumnDesc function in sardana

for a in ci.plot_axes:
                if a == '':
                    # skip plots against moveables in scans that do not involve
                    # them e.g. time scans
                    if len(ref_moveables) == 0:
                        continue
                    plotAxes.append(ref_moveables[i])
                    i += 1
                else:
                    plotAxes.append(a)
            try:
                value_ref_enabled = ci.value_ref_enabled
            except AttributeError:
                value_ref_enabled = False
            # create the ColumnDesc object
            column = ColumnDesc(name=ci.full_name,
                                label=ci.label,
                                dtype=ci.data_type,
                                shape=ci.shape,
                                instrument=instrumentFullName,
                                source=ci.source,
                                output=ci.output,
                                conditioning=ci.conditioning,
                                normalization=ci.normalization,
                                plot_type=ci.plot_type,
                                plot_axes=plotAxes,
                                data_units=ci.unit,
                                value_ref_enabled=value_ref_enabled)
            data_desc.append(column)
            counters.append(column.name)
        try:
            counters.remove(master['full_name'])

plot_axes=plotAxes,
                                data_units=ci.unit)
            data_desc.append(column)
            counters.append(column.name)
        try:
            counters.remove(master['full_name'])
        except ValueError:
            # timer may be disabled
            pass
        env['counters'] = counters

        for extra_column in self._extra_columns:
            data_desc.append(extra_column.getColumnDesc())
        # add extra columns
        data_desc += self._extrainfodesc
        data_desc.append(ColumnDesc(name='timestamp',
                                    label='dt', dtype='float64'))

        env['datadesc'] = data_desc

        # set the data compression default
        try:
            env['DataCompressionRank'] = self.macro.getEnv(
                'DataCompressionRank')
        except UnknownEnv:
            env['DataCompressionRank'] = -1

        # set the sample information
        # @todo: use the instrument API to get this info
        try:
            env['SampleInfo'] = self.macro.getEnv('SampleInfo')
        except UnknownEnv:

"""Expected keywords are:
            - model (str, mandatory): represents data source (ex.: a/b/c/d)
            - label (str, mandatory): column label
            - name (str, optional): unique name (defaults to model)
            - shape (seq, optional): data shape 
            - dtype (numpy.dtype, optional): data type
            - instrument (str, optional): full instrument name"""
        self._label = kwargs['label']
        self._model = kwargs['model']
        if not kwargs.has_key('dtype'):
            kwargs['dtype'] = self.getType()
        if not kwargs.has_key('shape'):
            kwargs['shape'] = self.getShape()
        if not kwargs.has_key('name'):
            kwargs['name'] = self._model
        self._column = ColumnDesc(**kwargs)

:param elements: (list) list of tuples of label,src for the
                         elements to read (can be pool elements or Taurus
                         attribute names).

        :return: (list) a list of :class:`ColumnDesc`,
                 each including a "pre_scan_value" attribute with the read
                 value for that attr
        """
        manager = self.macro.getManager()
        all_elements_info = manager.get_elements_with_interface('Element')
        ret = []
        for src, label in elements:
            try:
                if src in all_elements_info:
                    ei = all_elements_info[src]
                    column = ColumnDesc(name=ei.full_name,
                                        label=label,
                                        instrument=ei.instrument,
                                        source=ei.source)
                else:
                    column = ColumnDesc(name=src,
                                        label=label,
                                        source=src)

                # @Fixme: Tango-centric. It should work for any Taurus
                # Attribute
                v = PyTango.AttributeProxy(column.source).read().value
                column.pre_scan_value = v
                column.shape = np.shape(v)
                column.dtype = getattr(v, 'dtype', np.dtype(type(v))).name
                ret.append(column)
            except Exception:

'''reads the current values of the given elements
        
        :param elements: (list) list of tuples of label,src for the elements to read
                         (can be pool elements or Taurus attribute names).
        
        :return: (list) a list of :class:`ColumnDesc`, each including a 
                 "pre_scan_value" attribute with the read value for that attr
        '''
        manager = self.macro.getManager()
        all_elements_info = manager.get_elements_with_interface('Element')
        ret = []
        for src, label in elements:
            try:
                if src in all_elements_info:
                    ei = all_elements_info[src]
                    column = ColumnDesc(name=ei.full_name,
                                        label=label,
                                        instrument=ei.instrument,
                                        source=ei.source)
                else:
                    column = ColumnDesc(name=src,
                                        label=label,
                                        source=src)

                v = PyTango.AttributeProxy(column.source).read().value  #@Fixme: Tango-centric. It should work for any Taurus Attribute
                column.pre_scan_value = v
                column.shape = np.shape(v)
                column.dtype = getattr(v, 'dtype', np.dtype(type(v))).name
                ret.append(column)
            except:
                self.macro.warning('Error taking pre-scan snapshot of %s (%s)', label, src)
                self.debug('Details:', exc_info=1)

:param elements: (list) list of tuples of label,src for the
                         elements to read (can be pool elements or Taurus
                         attribute names).

        :return: (list) a list of :class:`ColumnDesc`,
                 each including a "pre_scan_value" attribute with the read
                 value for that attr
        """
        manager = self.macro.getManager()
        all_elements_info = manager.get_elements_with_interface('Element')
        ret = []
        for src, label in elements:
            try:
                if src in all_elements_info:
                    ei = all_elements_info[src]
                    column = ColumnDesc(name=ei.full_name,
                                        label=label,
                                        instrument=ei.instrument,
                                        source=ei.source)
                else:
                    column = ColumnDesc(name=src,
                                        label=label,
                                        source=src)

                # @Fixme: Tango-centric. It should work for any Taurus
                # Attribute
                v = PyTango.AttributeProxy(column.source).read().value
                column.pre_scan_value = v
                column.shape = np.shape(v)
                column.dtype = getattr(v, 'dtype', np.dtype(type(v))).name
                ret.append(column)
            except Exception:

instrumentFullName = self.macro.findObjs(instrument, type_class=Type.Instrument)[0].getFullName()
            except InterruptException:
                raise
            except:
                instrumentFullName = ''
            #substitute the axis placeholder by the corresponding moveable.
            plotAxes = []
            i = 0
            for a in ci.plot_axes:
                if a == '':
                    plotAxes.append(ref_moveables[i])
                    i += 1
                else: plotAxes.append(a)
                
            #create the ColumnDesc object
            column = ColumnDesc(name=ci.full_name,
                                label=ci.label,
                                dtype=ci.data_type,
                                shape=ci.shape,
                                instrument=instrumentFullName,
                                source=ci.source,
                                output=ci.output,
                                conditioning=ci.conditioning,
                                normalization=ci.normalization,
                                plot_type=ci.plot_type,
                                plot_axes=plotAxes,
                                data_units=ci.unit)
            data_desc.append(column)
            counters.append(column.name)
        counters.remove(master['full_name'])
        env['counters'] = counters

:return: (list) a list of :class:`ColumnDesc`, each including a 
                 "pre_scan_value" attribute with the read value for that attr
        '''
        manager = self.macro.getManager()
        all_elements_info = manager.get_elements_with_interface('Element')
        ret = []
        for src, label in elements:
            try:
                if src in all_elements_info:
                    ei = all_elements_info[src]
                    column = ColumnDesc(name=ei.full_name,
                                        label=label,
                                        instrument=ei.instrument,
                                        source=ei.source)
                else:
                    column = ColumnDesc(name=src,
                                        label=label,
                                        source=src)

                v = PyTango.AttributeProxy(column.source).read().value  #@Fixme: Tango-centric. It should work for any Taurus Attribute
                column.pre_scan_value = v
                column.shape = np.shape(v)
                column.dtype = getattr(v, 'dtype', np.dtype(type(v))).name
                ret.append(column)
            except:
                self.macro.warning('Error taking pre-scan snapshot of %s (%s)', label, src)
                self.debug('Details:', exc_info=1)
        return ret

data_units=ci.unit,
                                value_ref_enabled=value_ref_enabled)
            data_desc.append(column)
            counters.append(column.name)
        try:
            counters.remove(master['full_name'])
        except ValueError:
            # timer may be disabled
            pass
        env['counters'] = counters

        for extra_column in self._extra_columns:
            data_desc.append(extra_column.getColumnDesc())
        # add extra columns
        data_desc += self._extrainfodesc
        data_desc.append(ColumnDesc(name='timestamp',
                                    label='dt', dtype='float64'))

        env['datadesc'] = data_desc

        # set the data compression default
        try:
            env['DataCompressionRank'] = self.macro.getEnv(
                'DataCompressionRank')
        except UnknownEnv:
            env['DataCompressionRank'] = -1

        # set the sample information
        # @todo: use the instrument API to get this info
        try:
            env['SampleInfo'] = self.macro.getEnv('SampleInfo')
        except UnknownEnv: