input: Write a function to generate an HTML page containing a table with given employee data. The function should take in a list of dictionaries, where each dictionary represents an employee with keys 'Name', 'Job Title', 'Department', and 'Salary'. The function should return a string representing the complete HTML page with the table. If the input list is empty, the function should return an empty string.
  
  assert generate_employee_table([{'Name': 'John Doe', 'Job Title': 'Senior Developer', 'Department': 'IT', 'Salary': '$120,000'}, {'Name': 'Jane Doe', 'Job Title': 'Manager', 'Department': 'Finance', 'Salary': '$95,000'}, {'Name': 'Tim Smith', 'Job Title': 'Junior Developer', 'Department': 'IT', 'Salary': '$55,000'}]) == '<html>\n  <head>\n    <title>Employee Data</title>\n  </head>\n  <body>\n    <table>\n      <thead>\n        <tr>\n          <th>Name</th>\n          <th>Job Title</th>\n          <th>Department</th>\n          <th>Salary</th>\n        </tr>\n      </thead>\n      <tbody>\n        <tr>\n          <td>John Doe</td>\n          <td>Senior Developer</td>\n          <td>IT</td>\n          <td>$120,000</td>\n        </tr>\n        <tr>\n          <td>Jane Doe</td>\n          <td>Manager</td>\n          <td>Finance</td>\n          <td>$95,000</td>\n        </tr>\n        <tr>\n          <td>Tim Smith</td>\n          <td>Junior Developer</td>\n          <td>IT</td>\n          <td>$55,000</td>\n        </tr>\n      </tbody>\n    </table>\n  </body>\n</html>'
  assert generate_employee_table([]) == ''
output: def generate_employee_table(employees):
      if not employees:
          return ''
      
      html = '<html>\n  <head>\n    <title>Employee Data</title>\n  </head>\n  <body>\n    <table>\n      <thead>\n        <tr>\n          <th>Name</th>\n          <th>Job Title</th>\n          <th>Department</th>\n          <th>Salary</th>\n        </tr>\n      </thead>\n      <tbody>'
      
      for employee in employees:
          html += f'\n        <tr>\n          <td>{employee["Name"]}</td>\n          <td>{employee["Job Title"]}</td>\n          <td>{employee["Department"]}</td>\n          <td>{employee["Salary"]}</td>\n        </tr>'
      
      html += '\n      </tbody>\n    </table>\n  </body>\n</html>'
      
      return html