function getStringValue(value) {
  const expression = value.expression
  if (!expression) {
    return null
  }
  if (expression.type !== 'Literal') {
    return null
  }
  if (typeof expression.value === 'string') {
    return expression.value
  }
  return null
}
Get a string from given expression container node
@param {VExpressionContainer} value
@returns { string | null }