code: func ExplainExpressionList(exprs []Expression) []byte {
  	buffer := bytes.NewBufferString("")
  	for i, expr := range exprs {
  		buffer.WriteString(expr.ExplainInfo())
  		if i+1 < len(exprs) {
  			buffer.WriteString(", ")
  		}
  	}
  	return buffer.Bytes()
  }
docs: // ExplainExpressionList generates explain information for a list of expressions.