function isPureRenderDeclared(node) {
      let hasPR = false;
      if (node.value && node.value.elements) {
        for (let i = 0, l = node.value.elements.length; i < l; i++) {
          if (node.value.elements[i] && node.value.elements[i].name === 'PureRenderMixin') {
            hasPR = true;
            break;
          }
        }
      }

      return (
        !!node
        && node.key.name === 'mixins'
        && hasPR
      );
    }
Checks if we are declaring a PureRenderMixin mixin
@param {ASTNode} node The AST node being checked.
@returns {boolean} True if we are declaring a PureRenderMixin method, false if not.