D3js Cannot construct a LineSegment with two equal endpoints.

在使用D3画力导向图（force-directed graph）时，报错：

Cannot construct a LineSegment with two equal endpoints.

原因可能有：

一、存在不同节点的name值一样的情况

[
    {
        "name"    : "Fauchelevent", // Duplicated
        "type"    : "group0",
        "depends" : [
            "Valjean",
            "Javert"
        ]
    }, {
        "name"    : "Myriel",
        "type"    : "group1",
        "depends" : []
    }, {
        "name"    : "Fauchelevent", // Duplicated
        "type"    : "group1",
        "depends" : [
            "Myriel"
        ]
    }
]

二、存在自回环情况

也就是节点出来的线又指向了这个节点，也就是depends里面有这个节点的name值，

这种情况下从depends里面剔除这个节点的name值就好了，

stackoverflow也有这个问题：

https://stackoverflow.com/questions/28811950/uncaught-error-cannot-construct-a-line-segment-with-two-equal-endpoints