is ECharts 4.0 fully compatible with ECharts 3.0? For example, these two versions: 
 echarts3.6.1.js and echarts4.0.4.js 
 is ECharts 4.0 fully compatible with ECharts 3.0? For example, these two versions: 
 echarts3.6.1.js and echarts4.0.4.js 
there are some differences in code writing.
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