is_deletion property fails for _SingleBreakend

[rodoyle]

when self.is_deletion is invoked for this type of record, a TypeError is thrown

-> if len(self.REF) > len(alt_allele):
(Pdb) l
439             if self.is_indel:
440                 # just one alt allele
441                 alt_allele = self.ALT[0]
442                 if alt_allele is None:
443                     return True
444  ->             if len(self.REF) > len(alt_allele):
445                     return True
446                 else:
447                     return False
448             else:
449                 return False
(Pdb) self.ALT
[T.]
(Pdb) self.REF
'TGCCGCCAGCCCCCCGG'
(Pdb) len(self.ALT)
1
(Pdb) len(alt_allele)
*** TypeError: object of type '_SingleBreakend' has no len()

Should return TRUE.