code: def test_Ynm_c():
      th, ph = Symbol("theta", real=True), Symbol("phi", real=True)
      from sympy.abc import n, m
  
      assert Ynm_c(n, m, th, ph) == (-1) ** (2 * m) * exp(
          -2 * I * m * ph
      ) * Ynm(n, m, th, ph)
  
file_path: sympy/sympy/functions/special/tests/test_spherical_harmonics.py
imports: from sympy.core.function import diff
  from sympy.core.numbers import I, pi
  from sympy.core.symbol import Symbol
  from sympy.functions.elementary.complexes import conjugate
  from sympy.functions.elementary.exponential import exp
  from sympy.functions.elementary.miscellaneous import sqrt
  from sympy.functions.elementary.trigonometric import cos, cot, sin
  from sympy.functions.special.spherical_harmonics import Ynm, Znm, Ynm_c
label_desc: Use image node_id 2 for calling a global function with example usage: test_Ynm_c() without return types