def METHOD_NAME(blk, number_of_parallel_units=1):
    """
    General method for costing clarifiers. Costing is carried out
    using either the general_power_law form or the standard form which
    computes HRT, sizing costs, and chemical input costs.
    Args:
        number_of_parallel_units (int, optional) - cost this unit as
                    number_of_parallel_units parallel units (default: 1)
    """
    # Get cost method for this technology
    cost_method = blk.unit_model._get_unit_cost_method(blk)
    valid_methods = ["cost_power_law_flow", "cost_HRCS_clarifier"]
    if cost_method == "cost_power_law_flow":
        blk.unit_model.cost_power_law_flow(blk, number_of_parallel_units)
    elif cost_method == "cost_HRCS_clarifier":
        # NOTE: number of units does not matter for cost_HRCS_clarifier
        #       as its a linear function of membrane area
        blk.unit_model.cost_HRCS_clarifier(blk)
    else:
        raise KeyError(
            f"{cost_method} is not a relevant cost method for "
            f"{blk.unit_model._tech_type}. Specify one of the following "
            f"cost methods in the unit's YAML file: {valid_methods}"
        )