code: function findBRDA (source, blockNumber, branchNumber, lineNumber) {
    for (var i = 0; i < source.length; i++) {
      var brda = source[i]
      if (brda.blockNumber === blockNumber &&
        brda.branchNumber === branchNumber &&
        brda.lineNumber === lineNumber) {
        return brda
      }
    }
    return null
  }
docs: Find an existing BRDA record
  
  @param {BRDA[]}   source
  @param {number} blockNumber
  @param {number} branchNumber
  @param {number} lineNumber
  
  @returns {BRDA|null}