canDelete (annos, sel) {
    // When the cursor or selection is inside an existing annotation
    if (annos.length !== 1) return false
    const annoSel = annos[0].getSelection()
    return sel.isInsideOf(annoSel)
  }
Checks if annotation could be deleted.
    Cursor or selection must be inside an existing annotation.

    @param {Array} annos annotations
    @param {Object} sel selection

    @returns {Boolean} Whether or not annotation could be deleted.