code: def list(cls, session, first_name=None, last_name=None, email=None,
               modified_since=None):
          
          return super(Customers, cls).list(
              session,
              data=cls.__object__.get_non_empty_vals({
                  'firstName': first_name,
                  'lastName': last_name,
                  'email': email,
                  'modifiedSince': modified_since,
              })
          )
docs: List the customers.
  
          Customers can be filtered on any combination of first name, last name,
          email, and modifiedSince.
  
          Args:
              session (requests.sessions.Session): Authenticated session.
              first_name (str, optional): First name of customer.
              last_name (str, optional): Last name of customer.
              email (str, optional): Email address of customer.
              modified_since (datetime.datetime, optional): If modified after
                  this date.
  
          Returns:
              RequestPaginator(output_type=helpscout.models.Customer): Customers
                  iterator.