Check that the names of the objects are all different.

def check_valid_object_name(sequence):
    """Check that the names of the objects are all different."""
    names = []
    for o in sequence:
        if o.__name__ in names:
            raise ValueError(
                'A tallyable PyMC object called %s already exists. This will cause problems for some database backends.' %
                o.__name__)
        else:
            names.append(o.__name__)