<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def lookup(self, phonenumber, params=None):
 """Do a new lookup."""

        if params is None: params = {}
        return Lookup().load(self.request('lookup/' + str(phonenumber), 'GET', params))