text: #include<string>
  
  /*
  Write prototype for function get_gc_content that accepts
  a const reference string parameter and returns a double
  */
  
  
  /*
  Write prototype for function get_reverse_string that 
  accepts a string parameter and returns a string
  */
  
  
  /*
  Write prototype for function get_dna_complement that
  accepts a string and returns a string
  */
  
  // write function prototype for an int value-return function named factorial that accepts an int parameter named num. 
  int factorial (int num);
  
  // write function prototype for an int value-return function named gcd that accepts two int parameters.
  int gcd (int num1 , int num2);