old_contents: from __future__ import absolute_import
  
  
  def check(header, convention=None, dimensions=[0, 1]):
  
      ix = dimensions[0] + 1
      iy = dimensions[1] + 1
  
      ctypex = header['CTYPE%i' % ix]
      crvaly = header['CRVAL%i' % iy]
      crpixy = header['CRPIX%i' % iy]
      cdelty = header['CDELT%i' % iy]
  
      # Check for CRVAL2!=0 for CAR projection
      if ctypex[4:] == '-CAR' and crvaly != 0:
  
          if convention in ['wells', 'calabretta']:
              if convention == 'wells':
                  crpixy = crpixy - crvaly / cdelty
                  header.update('CRPIX%i' % iy, crpixy)
                  header.update('CRVAL%i' % iy, 0.0)
              else:
                  pass
          else:
              raise Exception('''WARNING: projection is Plate Caree (-CAR) and
              CRVAL2 is not zero. This can be intepreted either according to
              Wells (1981) or Calabretta (2002). The former defines the
              projection as rectilinear regardless of the value of CRVAL2,
              whereas the latter defines the projection as rectilinear only when
              CRVAL2 is zero. You will need to specify the convention to assume
              by setting either convention='wells' or convention='calabretta'
              when initializing the FITSFigure instance. ''')
  
      return header
  
new_contents: from __future__ import absolute_import
  
  
  def check(header, convention=None, dimensions=[0, 1]):
  
      ix = dimensions[0] + 1
      iy = dimensions[1] + 1
  
      ctypex = header['CTYPE%i' % ix]
      crvaly = header['CRVAL%i' % iy]
  
      # Check for CRVAL2!=0 for CAR projection
      if ctypex[4:] == '-CAR' and crvaly != 0:
  
          if convention in ['wells', 'calabretta']:
              if convention == 'wells':
                  try:
                      crpixy = header['CRPIX%i' % iy]
                      cdelty = header['CDELT%i' % iy]
                  except:
                      raise Exception("Need CDELT to be present for wells convention")
                  crpixy = crpixy - crvaly / cdelty
                  header.update('CRPIX%i' % iy, crpixy)
                  header.update('CRVAL%i' % iy, 0.0)
              else:
                  pass
          else:
              raise Exception('''WARNING: projection is Plate Caree (-CAR) and
              CRVAL2 is not zero. This can be intepreted either according to
              Wells (1981) or Calabretta (2002). The former defines the
              projection as rectilinear regardless of the value of CRVAL2,
              whereas the latter defines the projection as rectilinear only when
              CRVAL2 is zero. You will need to specify the convention to assume
              by setting either convention='wells' or convention='calabretta'
              when initializing the FITSFigure instance. ''')
  
      return header
  
subject: Fix check for Wells/Calabretta convention