Javascript cytoscape.js自动布局与固定节点

i'm making a graph layout with cytoscape.js. I want some nodes to have fixed positions. So in my current solution i use the cose layout of cytoscape and set postions for these nodes. It works but i have in my layout some node overlapping. I think the cose layout position the nodes regardless of the fixed nodes. Have anyone ideas how i can fix this? Thanks i'm making a graph layout with cytoscape.js. I