<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def source_range_slices(start, end, nr_var_dict):
 """ Given a range of source numbers, as well as a dictionary containing the numbers of each source, returns a dictionary containing slices for each source variable type. """


    return OrderedDict((k, slice(s,e,1))
        for k, (s, e)
        in source_range_tuple(start, end, nr_var_dict).iteritems())