code: def _is_simple_delta(delta, index):
      """
      Returns True if ``delta`` is a KroneckerDelta and is nonzero for a single
      value of the index ``index``.
      """
      if isinstance(delta, KroneckerDelta) and delta.has(index):
          p = (delta.args[0] - delta.args[1]).as_poly(index)
          if p:
              return p.degree() == 1
      return False
  
file_path: sympy/sympy/concrete/delta.py
imports: from .products import product
  from .summations import Sum, summation
  from sympy.core import Add, Mul, S, Dummy
  from sympy.core.cache import cacheit
  from sympy.core.sorting import default_sort_key
  from sympy.functions import KroneckerDelta, Piecewise, piecewise_fold
  from sympy.polys.polytools import factor
  from sympy.sets.sets import Interval
  from sympy.solvers.solvers import solve
label_desc: Use image node_id 4 for calling a global function with example usage: _is_simple_delta(delta, index) and returns: False, unknown