def METHOD_NAME(self, run_namespace=None):
    rates_var = self.variables["rates"]
    if isinstance(rates_var, Subexpression):
        # Check that the units of the expression make sense
        expr = rates_var.expr
        identifiers = get_identifiers(expr)
        variables = self.resolve_all(
            identifiers, run_namespace, user_identifiers=identifiers
        )
        unit = parse_expression_dimensions(rates_var.expr, variables)
        fail_for_dimension_mismatch(
            unit,
            Hz,
            "The expression provided for "
            "PoissonGroup's 'rates' "
            "argument, has to have units "
            "of Hz",
        )
    super().METHOD_NAME(run_namespace)