code: def check(self, line):
          
          if not isinstance(line, str):
              raise TypeError("Parameter 'line' not a 'string', is {0}".format(type(line)))
          if line in self.contents:
              return line
          return False
docs: Find first occurrence of 'line' in file.
  
          This searches each line as a whole, if you want to see if a substring is in a line, use .grep() or .egrep()
  
          If found, return the line; this makes it easier to chain methods.
  
          :param line: String; whole line to find.
          :return: String or False.