code: func (c *ColorM) SetElement(i, j int, element float32) *ColorM {
  	newC := &ColorM{
  		body:      make([]float32, 16),
  		translate: make([]float32, 4),
  	}
  	copy(newC.body, colorMIdentityBody)
  	copy(newC.translate, colorMIdentityTranslate)
  	if c.isInited() {
  		if c.body != nil {
  			copy(newC.body, c.body)
  		}
  		if c.translate != nil {
  			copy(newC.translate, c.translate)
  		}
  	}
  	if j < (ColorMDim - 1) {
  		newC.body[i+j*(ColorMDim-1)] = element
  	} else {
  		newC.translate[i] = element
  	}
  	return newC
  }
docs: // SetElement sets an element at (i, j).