def contraction(sheet, manager, **kwargs):
    """Single step contraction event."""
    contraction_spec = default_contraction_spec
    contraction_spec.update(**kwargs)
    face = contraction_spec["face"]

    if (sheet.face_df.loc[face, "area"] < contraction_spec["critical_area"]) or (
        sheet.face_df.loc[face, contraction_spec["contraction_column"]]
        > contraction_spec["max_contractility"]
    ):
        return
    increase(
        sheet,
        "face",
        face,
        contraction_spec["contractile_increase"],
        contraction_spec["contraction_column"],
        contraction_spec["multiply"],
    )