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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_sentences_for_agent(text, stmts, max_sentences=None):
 """Returns evidence sentences with a given agent text from a list of statements Parameters text : str An agent text stmts : list of :py:class:`indra.statements.Statement` INDRA Statements to search in for evidence statements. max_sentences : Optional[int/None] Cap on the number of evidence sentences to return. Default: None Returns ------- sentences : list of str Evidence sentences from the list of statements containing the given agent text. """

    sentences = []
    for stmt in stmts:
        for agent in stmt.agent_list():
            if agent is not None and agent.db_refs.get('TEXT') == text:
                sentences.append((stmt.evidence[0].pmid,
                                  stmt.evidence[0].text))
                if max_sentences is not None and \
                   len(sentences) >= max_sentences:
                    return sentences
    return sentences