<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def addfield(self, name, type, width=10):
 """ add a field to the vector layer Parameters name: str the field name type: int the OGR Field Type (OFT), e.g. ogr.OFTString. See `Module ogr <https://gdal.org/python/osgeo.ogr-module.html>`_. width: int the width of the new field (only for ogr.OFTString fields) Returns ------- """

        fieldDefn = ogr.FieldDefn(name, type)
        if type == ogr.OFTString:
            fieldDefn.SetWidth(width)
        self.layer.CreateField(fieldDefn)