code: def list_contacts(self, **kwargs):
          
  
          url = 'contacts.json?'
          if 'query' in kwargs.keys():
              filter_query = kwargs.pop('query')
              url = url + "query={}".format(filter_query)
  
          if 'state' in kwargs.keys():
              state_query = kwargs.pop('state')
              url = url + "state={}".format(state_query)    
  
          if 'letter' in kwargs.keys():
              name_query = kwargs.pop('letter')
              url = url + "letter={}".format(name_query)        
                  
          contacts = self._api._get(url)    
          return [Contact(**c['user']) for c in contacts]
docs: List all contacts, optionally filtered by a query. Specify filters as
          query keyword argument, such as: 
          
          query= email is abc@xyz.com,
          query= mobile is 1234567890,
          query= phone is 1234567890,
  
          contacts can be filtered by name such as;
          
          letter=Prenit
  
          Passing None means that no named filter will be passed to
          Freshdesk, which returns list of all contacts