def relative_subsequence(self, start, end):
if start < <NUM_LIT:1>:<EOL><INDENT>raise SequenceError("<STR_LIT>" +<EOL>str(start))<EOL><DEDENT>if end > self.ungapped_len:<EOL><INDENT>raise SequenceError("<STR_LIT>" +<EOL>str(end) + "<STR_LIT>" +<EOL>"<STR_LIT>" + self.ungapped_len +<EOL>"<STR_LIT:)>")<EOL><DEDENT>raise SequenceError("<STR_LIT>")<EOL>
Extract a subsequence from this sequence using coordinates that are
relative to the start (relative position 1) and end coordinates of the
sequence. For example:

  46  --> A--CTGC-TAGC-GATCGACT <--  62      subsequence(2,7) == CTGC-T

:param start:      the index marking the start (inclusive) of the
                   subsequence. This is a one-based index, and is in the
                   coordinate space of the sequence (i.e. from 1 to N,
                   where N is the number of non-gap nucleotides in the
                   sequence)
:param end:        the index marking the end (exclusive) of the
                   subsequence. This is a one-based index, and is in the
                   coordinate space of the sequence (i.e. from 1 to N,
                   where N is the number of non-gap nucleotides in the
                   sequence)

:return: a new sequence object that represents the subsequence
:rasie SequenceError: if the start coordinate is less than 1 or the end
                      coordinate is greater than the ungapped length of
                      this sequence.