class_docstr: The Prufer correspondence is an algorithm that describes the
  bijection between labeled trees and the Prufer code. A Prufer
  code of a labeled tree is unique up to isomorphism and has
  a length of n - 2.
  
  Prufer sequences were first used by Heinz Prufer to give a
  proof of Cayley's formula.
  
  References
  ==========
  
  .. [1] https://mathworld.wolfram.com/LabeledTree.html
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docstr: Generates the Prufer sequence that is -delta before the current one.
  
  Examples
  ========
  
  >>> from sympy.combinatorics.prufer import Prufer
  >>> a = Prufer([[0, 1], [1, 2], [2, 3], [1, 4]])
  >>> a.rank
  36
  >>> b = a.prev()
  >>> b
  Prufer([1, 2, 0])
  >>> b.rank
  35
  
  See Also
  ========
  
  prufer_rank, rank, next, size
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code: def prev(self, delta=1):
      """Generates the Prufer sequence that is -delta before the current one.
  
      Examples
      ========
  
      >>> from sympy.combinatorics.prufer import Prufer
      >>> a = Prufer([[0, 1], [1, 2], [2, 3], [1, 4]])
      >>> a.rank
      36
      >>> b = a.prev()
      >>> b
      Prufer([1, 2, 0])
      >>> b.rank
      35
  
      See Also
      ========
  
      prufer_rank, rank, next, size
  
      """
      return Prufer.unrank(self.rank - delta, self.nodes)
  
imports: from sympy.core import Basic
  from sympy.core.containers import Tuple
  from sympy.tensor.array import Array
  from sympy.core.sympify import _sympify
  from sympy.utilities.iterables import flatten, iterable
  from sympy.utilities.misc import as_int
  from collections import defaultdict
label_desc: Use image node_id 13 for calling the Prufer obj's underlying member method code with example usage: obj.prev(delta) and returns: Prufer