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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get(self, start, length):
 """ Fetch subsequence starting at position `start` with length `length`. This method is picky about parameters, the requested interval must have non-negative length and fit entirely inside the NIB sequence, the returned string will contain exactly 'length' characters, or an AssertionError will be generated. """

        # Check parameters
        assert length >= 0, "Length must be non-negative (got %d)" % length 
        assert start >= 0,"Start must be greater than 0 (got %d)" % start
        assert start + length <= self.length, \
            "Interval beyond end of sequence (%s..%s > %s)" % ( start, start + length, self.length )
        # Fetch sequence and reverse complement if necesary
        if not self.revcomp:
            return self.raw_fetch( start, length )
        if self.revcomp == "-3'":
            return self.reverse_complement(self.raw_fetch(start,length))
        assert self.revcomp == "-5'", "unrecognized reverse complement scheme"
        start = self.length - (start+length)
        return self.reverse_complement(self.raw_fetch(start,length))