Indentation has has both tabs and spaces in it. Programmers should use either tabs or spaces, but not both.

Anti-pattern

Note: The character represents a space and the character represents a tab.

In this example, the third line contains four spaces and two tabs.

def get_name(self):
    if self.first_name and self.last_name:
••••→  return self.first_name + ' ' + self.last_name
    else:
        return self.last_name

Best practice

Change the line to use spaces only.

def get_name(self):
    if self.first_name and self.last_name:
••••••••return self.first_name + ' ' + self.last_name
    else:
        return self.last_name