'This method gives the names of each field in the feature vector in the
order in which they are returned. For example, \'xpos\' or \'width\''

def getFieldNames(self):

    retVal = []
    retVal.append('area    over    perim')
    retVal.append('AR')
    retVal.append('Hu0')
    retVal.append('Hu1')
    retVal.append('Hu2')
    retVal.append('Hu3')
    retVal.append('Hu4')
    retVal.append('Hu5')
    retVal.append('Hu6')
    return retVal
