def to_cortex(c):
if is_cortex(c): return c<EOL>elif pimms.is_vector(c) and len(c) == <NUM_LIT:2>:<EOL><INDENT>(s,h) = c<EOL>if is_subject(s) and pimms.is_str(h):<EOL><INDENT>if h in s.hemis: return s.hemis[h]<EOL>else: raise ValueError('<STR_LIT>' % h)<EOL><DEDENT><DEDENT>raise ValueError('<STR_LIT>')<EOL>
to_cortex(c) yields a Cortex object if the argument c can be coerced to one and otherwise raises
  an error.

An object can be coerced to a Cortex object if:
  * it is a cortex object
  * it is a tuple (subject, h) where subject is a subject object and h is a subject hemisphere.