title: How to pass data to SectionList?
body: <p>I am really confused as I don't understand how to pass an array to the SectionList. When I try this one everything is ok </p>
  
  <pre><code> &lt;SectionList
       renderItem={({item}) =&gt; &lt;View&gt;&lt;Text&gt; title={item.title}&lt;/Text&gt;&lt;/View&gt;}
        renderSectionHeader={({section}) =&gt; 
            &lt;View&gt;&lt;Text&gt; title={section.key}&lt;/Text&gt;&lt;/View&gt;}
            sections={[
                 {data: [{title:123},{title:"aaa"}], key: "aaa"},
                 data: [{title:333},{title:"bbbb"}], key: "bbb"},
                 {data: [{title:123},{title:"aaa"}], key: "ccc"},
            ]}
            /&gt;
  </code></pre>
  
  <p>But if I try to use a function (as I understand it is totally the same), I got an error "props.sections.reduce is not a function". How to pass an array with function to the SectionList? Thanks</p>
  
  <pre><code> sections={()=&gt;[
          {data: [{title:123},{title:"aaa"}], key: "aaa"},
           data: [{title:333},{title:"bbbb"}], key: "bbb"},
           {data: [{title:123},{title:"aaa"}], key: "ccc"},
          ]}
    /&gt;
  </code></pre>