Cannot set vertical margin between the items in the iron-list.

[Krishuthapa]

Description

Cannot set vertical margin between the items in the iron-list.

I have used iron-list in LitElement which contains the array of a custom component.

 <iron-list .items="${this.filteredModuleList}" as="item">
        <template>
          <campaign-card
            campaignId$="{{item.id}}"
            name$="{{item.name}}"
            scientist$="{{item.scientist.name}}"
            createdDate$="{{item.created_date}}"
            campaignStatus$="{{item.status}}"
            synthesisType$="{{item.synthesis_type.name}}"
            targetId$="{{item.target.id}}"
            cardTopic="${this.cardTopic}"
          >
          </campaign-card>
        </template>
      </iron-list>

I want to set the vertical margin between these elements.But it does not work. How can I set the margin-top and margin-bottom.