Helper function for random generators.

def _random_helper(random, sampler, params, shape, dtype, kwargs):
    """Helper function for random generators."""
    if isinstance(params[0], Symbol):
        for i in params[1:]:
            assert isinstance(i, Symbol), \
                "Distribution parameters must all have the same type, but got " \
                "both %s and %s."%(type(params[0]), type(i))
        return sampler(*params, shape=shape, dtype=dtype, **kwargs)
    elif isinstance(params[0], numeric_types):
        for i in params[1:]:
            assert isinstance(i, numeric_types), \
                "Distribution parameters must all have the same type, but got " \
                "both %s and %s."%(type(params[0]), type(i))
        return random(*params, shape=shape, dtype=dtype, **kwargs)

    raise ValueError("Distribution parameters must be either Symbol or numbers, "
                     "but got %s."%type(params[0]))