new_contents: """
  intervaltree: A mutable, self-balancing interval tree for Python 2 and 3.
  Queries may be by point, by range overlap, or by range envelopment.
  
  Test module: IntervalTree, insertion and removal of float intervals
  Submitted as issue #26 (Incorrect KeyError) by sciencectn
  
  Copyright 2013-2014 Chaim-Leib Halbert
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
  
     http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  """
  from __future__ import absolute_import
  from intervaltree import IntervalTree
  # from test.intervaltrees import trees
  import pytest
  
  
  def test_original_sequence():
      t = IntervalTree()
      t.addi(17.89,21.89)
      t.addi(11.53,16.53)
      t.removei(11.53,16.53)
      t.removei(17.89,21.89)
      t.addi(-0.62,4.38)
      t.addi(9.24,14.24)
      t.addi(4.0,9.0)
      t.removei(-0.62,4.38)
      t.removei(9.24,14.24)
      t.removei(4.0,9.0)
      t.addi(12.86,17.86)
      t.addi(16.65,21.65)
      t.removei(12.86,17.86)
  
  
  def test_debug_sequence():
      t = IntervalTree()
      t.verify()
      t.addi(17.89,21.89)
      t.verify()
      t.addi(11.53,16.53)
      t.verify()
      t.removei(11.53,16.53)
      t.verify()
      t.removei(17.89,21.89)
      t.verify()
      t.addi(-0.62,4.38)
      t.verify()
      t.addi(9.24,14.24)
      t.print_structure()
      # Node<-0.62, depth=2, balance=1>
      #  Interval(-0.62, 4.38)
      # >:  Node<9.24, depth=1, balance=0>
      #      Interval(9.24, 14.24)
      t.verify()
  
      t.addi(4.0,9.0)  # This line breaks the invariants, leaving an empty node
      t.print_structure()
      t.verify()
      t.removei(-0.62,4.38)
      t.verify()
      t.removei(9.24,14.24)
      t.verify()
      t.removei(4.0,9.0)
      t.verify()
      t.addi(12.86,17.86)
      t.verify()
      t.addi(16.65,21.65)
      t.verify()
      t.removei(12.86,17.86)
  
  
  if __name__ == "__main__":
      # pytest.main([__file__, '-v'])
      test_debug_sequence()
  
subject: test for issue #26