Pass in a dictionary of parameters, loop through them and build a payload containing,
    parameters who's values are not None.

def _loop_payload(params):
    '''
    Pass in a dictionary of parameters, loop through them and build a payload containing,
    parameters who's values are not None.
    '''

    #construct the payload
    payload = {}

    #set the payload
    for param, value in six.iteritems(params):
        if value is not None:
            payload[param] = value

    return payload