code: function findStartLine(fileLines, functionName, lineNumber) {
          var startLine = lineNumber - 1
          while(true) {
              if(startLine < 0) {
                  return 'lineOfCodeNotFound' // something went wrong if this is being returned (the functionName wasn't found above - means you didn't get the function name right)
              }
  
              var line = fileLines[startLine]
              if(line === undefined) {
                  return 'sourceNotAvailable'
              }
  
              //lines.push(line.trim())
              var containsFunction = line.indexOf(functionName) !== -1
              if(containsFunction) {
                  return startLine
              }
  
              startLine--
          }
      }
docs: finds the line a function started on given the file's lines, and the stack trace line number (and function name) returns undefined if something went wrong finding the startline