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