code: def E_n(n, a, mass):
      """
      Returns the Energy psi_{n} for a 1d potential hole with infinity borders
  
      ``n``
          the "principal" quantum number. Corresponds to the number of nodes in
          the wavefunction.  n >= 0
      ``a``
          width of the well. a > 0
      ``mass``
          mass.
      """
      return ((n * pi / a) ** 2) / mass
  
imports: from sympy.core import pi
  from sympy import Integral, var, S
  from sympy.functions import sin, sqrt
label_desc: Use image node_id 2 for calling a global function with example usage: E_n(n, a, mass) and returns: unknown