code: function isUsingIterationVar (vFor, vBindKey) {
    if (vBindKey.value == null) {
      return false
    }
    const references = vBindKey.value.references
    const variables = vFor.parent.parent.variables
    return references.some(reference =>
      variables.some(variable =>
        variable.id.name === reference.id.name &&
              variable.kind === 'v-for'
      )
    )
  }
docs: ------------------------------------------------------------------------------ Helpers ------------------------------------------------------------------------------ 
  Check whether the given attribute is using the variables which are defined by `v-for` directives.
  @param {ASTNode} vFor The attribute node of `v-for` to check.
  @param {ASTNode} vBindKey The attribute node of `v-bind:key` to check.
  @returns {boolean} `true` if the node is using the variables which are defined by `v-for` directives.