parameters: (A,lenient=_C)
docstring: \n        Extract the image metadata by reading\n        the initial part of the PNG file up to\n        the start of the ``IDAT`` chunk.\n        All the chunks that precede the ``IDAT`` chunk are\n        read and either processed for metadata or discarded.\n\n        If the optional `lenient` argument evaluates to `True`,\n        checksum failures will raise warnings rather than exceptions.\n
docstring_summary: \n        Extract the image metadata by reading\n        the initial part of the PNG file up to\n        the start of the ``IDAT`` chunk.\n        All the chunks that precede the ``IDAT`` chunk are\n        read and either processed for metadata or discarded.\n\n        If the optional `lenient` argument evaluates to `True`,\n        checksum failures will raise warnings rather than exceptions.\n
docstring_tokens: \ n Extract the image metadata by reading \ n the initial part of the PNG file up to \ n the start of the IDAT chunk . \ n All the chunks that precede the IDAT chunk are \ n read and either processed for metadata or discarded . \ n \ n If the optional lenient argument evaluates to True \ n checksum failures will raise warnings rather than exceptions . \ n
function: def preamble(A,lenient=_C):
  		'\n        Extract the image metadata by reading\n        the initial part of the PNG file up to\n        the start of the ``IDAT`` chunk.\n        All the chunks that precede the ``IDAT`` chunk are\n        read and either processed for metadata or discarded.\n\n        If the optional `lenient` argument evaluates to `True`,\n        checksum failures will raise warnings rather than exceptions.\n        ';A.validate_signature()
  		while _H:
  			if not A.atchunk:
  				A.atchunk=A._chunk_len_type()
  				if A.atchunk is _A:raise FormatError('This PNG file has no IDAT chunks.')
  			if A.atchunk[1]==_J:return
  			A.process_chunk(lenient=lenient)
function_tokens: def preamble ( A , lenient = _C ) : A . validate_signature ( ) while _H : if not A . atchunk : A . atchunk = A . _chunk_len_type ( ) if A . atchunk is _A : raise FormatError ( 'This PNG file has no IDAT chunks.' ) if A . atchunk [ 1 ] == _J : return A . process_chunk ( lenient = lenient )