code: function _flattenProofBranches(proofBranchArray) {
    let flatProofAnchors = []
  
    _forEach(proofBranchArray, proofBranch => {
      let anchors = proofBranch.anchors
      _forEach(anchors, anchor => {
        let flatAnchor = {}
        flatAnchor.branch = proofBranch.label || undefined
        flatAnchor.uri = anchor.uris[0]
        flatAnchor.type = anchor.type
        flatAnchor.anchor_id = anchor.anchor_id
        flatAnchor.expected_value = anchor.expected_value
        flatProofAnchors.push(flatAnchor)
      })
      if (proofBranch.branches) {
        flatProofAnchors = flatProofAnchors.concat(
          _flattenProofBranches(proofBranch.branches)
        )
      }
    })
    return flatProofAnchors
  }
docs: Flatten an Array of proof branches where each proof anchor in
  each branch is represented as an Object with all relevant data for that anchor.
  
  @param {Array} proofBranchArray - An Array of branches for a given level in a proof
  @returns {Array} An Array of flattened proof anchor objects for each branch