The analyse_text method for MojoLexer in https://github.com/pygments/pygments/blob/master/pygments/lexers/mojo.py#L701 is a near-copy of that from PythonLexer in https://github.com/pygments/pygments/blob/master/pygments/lexers/python.py#L408.

A code sample that contains import foo thus evaluates as Mojo rather than Python. Python is more likely, so Mojo should have a lower priority.