code: def find(find_seq, elem_list):
          
          seq_pos = 0
          for index, elem in enumerate(elem_list):
              if Sequence.match(elem, find_seq[seq_pos]):
                  seq_pos += 1
                  if seq_pos == len(find_seq):  # found matching sequence
                      return index - seq_pos + 1
              else:  # exited sequence
                  seq_pos = 0
          raise LookupError('Failed to find sequence in elem_list')
docs: Return the first position in elem_list where find_seq starts