<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def remove_isoforms(ids):
 """ This is more or less a hack to remove the GMAP multiple mappings. Multiple GMAP mappings can be seen given the names .mrna1, .mrna2, etc. """

    key = lambda x: x.rsplit(".", 1)[0]
    iso_number = lambda x: get_number(x.split(".")[-1])
    ids = sorted(ids, key=key)
    newids = []
    for k, ii in groupby(ids, key=key):
        min_i = min(list(ii), key=iso_number)
        newids.append(min_i)
    return newids