<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def start(self, network_name, trunk_name, trunk_type):
 """Starts DHCP server process. in network_name of type str Name of internal network DHCP server should attach to. in trunk_name of type str Name of internal network trunk. in trunk_type of type str Type of internal network trunk. raises :class:`OleErrorFail` Failed to start the process. """

        if not isinstance(network_name, basestring):
            raise TypeError("network_name can only be an instance of type basestring")
        if not isinstance(trunk_name, basestring):
            raise TypeError("trunk_name can only be an instance of type basestring")
        if not isinstance(trunk_type, basestring):
            raise TypeError("trunk_type can only be an instance of type basestring")
        self._call("start",
                     in_p=[network_name, trunk_name, trunk_type])