def parse_revision_spec(self, revisions=[]):
        n_revisions = len(revisions)

        if n_revisions == 0:
            raise InvalidRevisionSpecError(
                'Either a changeset or a branch must be specified')
        elif n_revisions == 1:
            return {
                'base': None,
                'tip': revisions[0],
            }
        else:
            raise TooManyRevisionsError
Create a random model by convolving a kernel with a
dataset/ETHPy150Open reviewboard/rbtools/rbtools/clients/plastic.py/PlasticClient.parse_revision_spec--crossover with--dataset/ETHPy150Open simpeg/simpeg/SimPEG/Utils/ModelBuilder.py/randomModel