text: 
  import { LitElement, html, css } from 'lit-element';
  import { BsContentRebootCss } from '@lit-element-bootstrap/content/bs-content-reboot-css.js';
  
  export class BsCardColumns extends LitElement {
      
      static get styles() {
          return [
              BsContentRebootCss,
              css`
                  :host {
                      display: block;
                  }
                  
                  :host ::slotted(bs-card) {
                      margin-bottom: 0.75rem;
                  }
                  
                  @media (min-width: 576px) {
                      
                      :host {
                          -webkit-column-count: var(--card-column-count, 3);
                          -moz-column-count: var(--card-column-count, 3);
                          column-count: var(--card-column-count, 3);
                          -webkit-column-gap: var(--card-column-gap, 1.25rem);
                          -moz-column-gap: var(--card-column-gap, 1.25rem);
                          column-gap: var(--card-column-gap, 1.25rem);
                          orphans: 1;
                          widows: 1;
                      }
                      
                      :host ::slotted(bs-card) {
                          display: inline-block;
                          width: 100%;
                      }
                  }
              `
          ];
      }
      
      render() {
          return html`
              <slot></slot>
          `;
      }
  };
  
  if (!window.customElements.get("bs-card-columns")) 
      window.customElements.define('bs-card-columns', BsCardColumns);