code: ####Please do not remove lines below####
  from lmfit import Parameters
  import numpy as np
  import sys
  import os
  sys.path.append(os.path.abspath('.'))
  sys.path.append(os.path.abspath('./Functions'))
  sys.path.append(os.path.abspath('./Fortran_rountines'))
  
  ####Please do not remove lines above####
  
  ####Import your modules below if needed####
  from xraydb import XrayDB
  #from pyEQL import chemical_formula
  
  
  class SphericalShell_expDecay: #Please put the class name same as the function name
      No = 6.023e23  # Avagadro number
      re2= (2.817e-5)**2 # Square of classical electron radius in Angs^2
      def __init__(self, x=0, rmin=0.0, rmax=30.0, Nr=31, Rc=10.0, strho=1.0, tst=2.0, lrho=0.5, lexp=10.0, rhosol=0.0, norm=1.0, bkg=0.0, mpar={}):
          """
          Documentation
          x     	: independent variable in the form of a scalar or an array
          Rc    	: Radial distance in Angstroms after which the solvent contribution starts
          strho 	: Concentration of the ions of interest in the stern layer in Molar
          tst   	: Thickness of stern layer in Angstroms
          lrho  	: The maximum concentration of the diffuse layer in Molars
          lexp  	: The decay length of the diffuse layer assuming exponential decay
          rhosol	: The surrounding bulk density
          norm  	: Density of particles in Moles/Liter
          bkg  	: Constant background
          """
          if type(x)==list:
              self.x=np.array(x)
          else:
              self.x=x
          self.rmin=rmin
          self.rmax=rmax
          self.Nr=Nr
          self.Rc=Rc
          self.strho=strho
          self.tst=tst
          self.lrho=lrho
          self.lexp=lexp
          self.rhosol=rhosol
          self.norm=norm
          self.bkg=bkg
          self.__mpar__=mpar #If there is any multivalued parameter
          self.choices={} #If there are choices available for any fixed parameters
          self.__xrdb__=XrayDB()
          self.init_params()
  
      def init_params(self):
          """
          Define all the fitting parameters like
          self.param.add('sig',value=0,vary=0)
          """
          self.params=Parameters()
          self.params.add('Rc',value=self.Rc,vary=0,min=-np.inf,max=np.inf,expr=None,brute_step=0.1)
          self.params.add('strho', value=self.strho, vary=0, min=-np.inf, max=np.inf, expr=None, brute_step=0.1)
          self.params.add('tst', value=self.tst, vary=0, min=-np.inf, max=np.inf, expr=None, brute_step=0.1)
          self.params.add('lrho', value=self.lrho, vary=0, min=-np.inf, max=np.inf, expr=None, brute_step=0.1)
          self.params.add('lexp', value=self.lexp, vary=0, min=-np.inf, max=np.inf, expr=None, brute_step=0.1)
          self.params.add('norm', value=self.norm, vary=0, min=-np.inf, max=np.inf, expr=None, brute_step=0.1)
          self.params.add('bkg', value=self.bkg, vary=0, min=-np.inf, max=np.inf, expr=None, brute_step=0.1)
  
  
  
      def solrho(self, r, Rp=100.0, Rc=12.5, strho=1.0, tst=2.0, lrho=0.5, lexp=10.0, rhosol=0.0):
          """
          Calculates the electron density for the distribution of ions as a function of radial distance surrounding a spherical particle
  
          Rp     :: Radius of the sphere in Angstroms enclosing the spherical particle
          Rc     :: Radial distance in Angstroms after which the solvent contribution starts
          strho    :: Concentration of the ions of interest in the stern layer in Molar
          tst      :: Thickness of stern layer in Angstroms
          lrho     :: The maximum concentration of the diffuse layer in Molars
          lexp     :: The decay length of the diffuse layer assuming exponential decay
          rhosol   :: The surrounding bulk density
          """
          R1=Rc
          R2=Rc+tst
          #integral=np.sum([r1**2*np.exp(-(r1-R2)/lexp) for r1 in np.linspace(R2,Rp,1001)])*(Rp-R2)/1000
          integral=lexp*(R2**2*np.exp(-R2/lexp)-Rp**2*np.exp(-Rp/lexp))+2*lexp**2*(R2*np.exp(-R2/lexp)-Rp*np.exp(-Rp/lexp))+2*lexp**3*(np.exp(-Rp/lexp)-np.exp(-R2/lexp))
          rhos=(rhosol*(Rp**3-R1**3)-strho*(R2**3-R1**3)-3*lrho*integral*np.exp(R2/lexp))/(Rp**3-R2**3)
          self.output_params['scaler_parameters']['rho_bulk']=rhos
          stern = np.where(r > R1, strho, 0.0) * np.where(r > R2, 0.0, 1.0)
          diffuse = np.where(r > R2, lrho * np.exp(-(r - R2) / lexp) + rhos, 0.0)
          rho = (stern + diffuse)
          return rho # in Moles/Liter
  
  
      def calc_form(self, q, r, rho):
          """
          Calculates the isotropic form factor using the isotropic electron density as a funciton of radial distance
  
          q       :: scaler or array of reciprocal reciprocal wave vector in inv. Angstroms at which the form factor needs to be calculated in
          r       :: array of radial distances at which the element/ion density in known in Angstroms
          rho     :: array of element/ion densities as a function of radial distance in el/Angstroms^3. Note: The electron density should decay to zero at the last radial distance
          """
          dr = r[1] - r[0]
          form = np.zeros_like(q)
          rho = (rho - rho[-1])* self.No/1e27 #converting it to moles/Angs^3
          for r1, rho1 in zip(r, rho):
              form = form + 4 * np.pi * r1 * rho1 * np.sin(q * r1) / q
          form = (np.absolute(form) * dr)**2
          return self.re2 * form * 1e-16 * self.No / 1e3 # in cm^-1
  
      def y(self):
          """
          Define the function in terms of x to return some value
          """
          self.output_params={}
          self.output_params['scaler_parameters']={}
          r=np.linspace(self.rmin, self.rmax, self.Nr)
          strho=self.params['strho'].value
          tst=self.params['tst'].value
          lrho=self.params['lrho'].value
          lexp=self.params['lexp'].value
          #rhosol=self.params['rhosol'].value
          norm=self.params['norm'].value
          bkg=self.params['bkg'].value
          Rc = self.params['Rc'].value
          Rp=(3/(4*np.pi*norm*6.022e23))**(1.0/3.0)*1e9
          rho=self.solrho(r, Rp=Rp, Rc=Rc, strho=strho, tst=tst, lrho=lrho, lexp=lexp, rhosol=self.rhosol)
          self.output_params['Electron_Density']={'x':r,'y':rho}
          self.output_params['scaler_parameters']['Rp']=Rp
          form=norm*self.calc_form(self.x,r,rho)+bkg
          return form
  
  if __name__=='__main__':
      x=np.arange(0.001,1.0,0.1)
      fun=SphericalShell_expDecay(x=x)
      print(fun.y())
  
apis: numpy.zeros_like numpy.exp numpy.arange numpy.absolute numpy.array numpy.sin numpy.where numpy.linspace