code: def fourier_function(freq_dict, x):
      r"""Function of the form :math:`\sum c_n e^{inx}` to construct
      and evaluate a Fourier series given
      a dictionary of frequencies and their coefficients.
  
      Args:
          freq_dict (dict[int, float]): Pairs of positive integer frequencies and corresponding
              Fourier coefficients.
  
      Returns:
          float: output of the function
      """
      result = 0
  
      # Handle 0 coefficient separately
      if 0 in freq_dict.keys():
          result = freq_dict[0]
  
      _sum = sum(
          coeff * np.exp(1j * freq * x)
          for freq, coeff in freq_dict.items()
          if freq != 0
      )
      result += _sum + np.conj(_sum)
      return result.real
  
imports: from functools import partial
  import pytest
  import pennylane
  from pennylane import numpy
  from pennylane.fourier import coefficients
label_desc: Use image node_id 1 for calling a global function with example usage: fourier_function(freq_dict, x) and returns: result