class AbstractContract implements Contract {
    /** associated binding */
    protected Set<Binding>        bindings      = new HashSet<>(2);
    /** unique id */
    protected String              uniqueId;
    /** interface class type */
    protected Class<?>            interfaceType;
    /** interface class type name*/
    protected String              interfaceTypeCanonicalName;
    /** interface mode */
    protected InterfaceMode       interfaceMode = InterfaceMode.spring;
    /** properties of contract */
    protected Map<String, String> property      = new HashMap<>();

    protected AbstractContract(String uniqueId, Class<?> interfaceType) {
        this.uniqueId = Objects.requireNonNullElse(uniqueId, "");
        this.interfaceType = interfaceType;
        this.interfaceTypeCanonicalName = interfaceType.getCanonicalName();
    }

    protected AbstractContract(String uniqueId, Class<?> interfaceType, InterfaceMode interfaceMode) {
        this(uniqueId, interfaceType);
        this.interfaceMode = interfaceMode;
    }

    protected AbstractContract(String uniqueId, Class<?> interfaceType,
                               InterfaceMode interfaceMode, Map<String, String> property) {
        this(uniqueId, interfaceType, interfaceMode);
        this.property = property;
    }

    @Override
    public <T extends Binding> void addBinding(T binding) {
        this.bindings.add(binding);
    }

    @Override
    public <T extends Binding> void addBinding(Set<T> bindings) {
        this.bindings.addAll(bindings);
    }

    @Override
    public Binding getBinding(BindingType bindingType) {
        for (Binding binding : this.bindings) {
            if (binding != null && binding.getBindingType() == bindingType) {
                return binding;
            }
        }
        return null;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Set<Binding> getBindings() {
        return this.bindings;
    }

    @Override
    public boolean hasBinding() {
        return this.bindings.size() > 0;
    }

    @Override
    public String getUniqueId() {
        return uniqueId;
    }

    @Override
    public InterfaceMode getInterfaceMode() {
        return this.interfaceMode;
    }

    @Override
    public Class<?> getInterfaceType() {
        return interfaceType;
    }

    @Override
    public String getProperty(String key) {<FILL_FUNCTION_BODY>}

    @Override
    public Map<String, String> getProperty() {
        return property;
    }

    @Override
    public String getInterfaceTypeCanonicalName() {
        return interfaceTypeCanonicalName;
    }
}

        if (property == null) {
            return null;
        }

        return property.get(key);
    
<no_super_class>