title: Get all elementary flows generated by an activity in Brightway
body: <p>I would like to access to all elementary flows generated by an activity in Brightway in a table that would gather the flows and the amounts.</p>
  <p>Let's assume a random activity :</p>
  <pre><code>lca=bw.LCA({random_act:2761,method)
  lca.lci()
  lca.lcia()
  lca.inventory 
  </code></pre>
  <p>I have tried several ways but none works :</p>
  <ul>
  <li><p>I have tried to export my lci with brightway2-io but some errors appear that i cannot solve :
  <code>bw2io.export.excel.lci_matrices_to_excel(db_name)</code> returns an error when computing the biosphere matrix data for a specific row :</p>
  <pre><code>--&gt; 120     bm_sheet.write_number(bio_lookup[row] + 1, act_lookup[col] + 1, value)
      122 COLUMNS = (
      123     u&quot;Index&quot;,
      124     u&quot;Name&quot;,
     (...)
      128     u&quot;Location&quot;,
      129 )
      131 tech_sheet = workbook.add_worksheet(&quot;technosphere-labels&quot;)
  
  KeyError: 1757 
  
  </code></pre>
  </li>
  <li><p>I try to get manually the amount of a specific elementary flow. For example, let's say I want to compute the total amount of Aluminium needed for the activity. To do so, i try this:</p>
  <p><code>flow_Al=Database(&quot;biosphere3&quot;).search(&quot;Aluminium, in ground&quot;)</code></p>
  </li>
  </ul>
  <p>(I only want the resource Aluminium that is extracted as a ore, from the ground)</p>
  <pre><code>amount_Al=0
  row = lca.biosphere_dict[flow_Al]
  col_indices = lca.biosphere_matrix[row, :].tocoo()
  amount_consumers_lca = [lca.inventory[row, index] for index in col_indices.col]
  for j in amount_consumers_lca:
      amount_Al=amount_Al+j
  amount_Al`
  </code></pre>
  <p>This works but the final amount is too low and probably isn't what i'm looking for...</p>
  <p>How can I solve this ?</p>
  <p>Thank you</p>